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0.8em;font-weight:bold}.mw-parser-output .sidebar-collapse .sidebar-above,.mw-parser-output .sidebar-collapse .sidebar-below{border-top:1px solid #aaa;border-bottom:1px solid #aaa}.mw-parser-output .sidebar-navbar{text-align:right;font-size:115%;padding:0 0.4em 0.4em}.mw-parser-output .sidebar-list-title{padding:0 0.4em;text-align:left;font-weight:bold;line-height:1.6em;font-size:105%}.mw-parser-output .sidebar-list-title-c{padding:0 0.4em;text-align:center;margin:0 3.3em}@media(max-width:640px){body.mediawiki .mw-parser-output .sidebar{width:100%!important;clear:both;float:none!important;margin-left:0!important;margin-right:0!important}}body.skin--responsive .mw-parser-output .sidebar a>img{max-width:none!important}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}}</style><table class="sidebar nomobile nowraplinks hlist"><tbody><tr><th class="sidebar-title"><a href="/wiki/HTTP" title="HTTP">HTTP</a></th></tr><tr><td class="sidebar-image"><span typeof="mw:File"><a href="/wiki/File:HTTP_logo.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5b/HTTP_logo.svg/180px-HTTP_logo.svg.png" decoding="async" width="180" height="96" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5b/HTTP_logo.svg/270px-HTTP_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5b/HTTP_logo.svg/360px-HTTP_logo.svg.png 2x" data-file-width="512" data-file-height="274" /></a></span></td></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/HTTP_persistent_connection" title="HTTP persistent connection">Persistence</a></li> <li><a href="/wiki/HTTP_compression" title="HTTP compression">Compression</a></li> <li><a href="/wiki/HTTPS" title="HTTPS">HTTPS</a></li> <li><a href="/wiki/QUIC" title="QUIC">QUIC</a></li></ul></td> </tr><tr><th class="sidebar-heading"> <a href="/wiki/HTTP#Request_methods" title="HTTP">Request methods</a></th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/HTTP#Request_methods" title="HTTP">OPTIONS</a></li> <li><a href="/wiki/HTTP#Request_methods" title="HTTP">GET</a></li> <li><a href="/wiki/HTTP#Request_methods" title="HTTP">HEAD</a></li> <li><a href="/wiki/POST_(HTTP)" title="POST (HTTP)">POST</a></li> <li><a href="/wiki/HTTP#Request_methods" title="HTTP">PUT</a></li> <li><a href="/wiki/HTTP#Request_methods" title="HTTP">DELETE</a></li> <li><a href="/wiki/HTTP#Request_methods" title="HTTP">TRACE</a></li> <li><a href="/wiki/HTTP#Request_methods" title="HTTP">CONNECT</a></li> <li><a href="/wiki/PATCH_(HTTP)" title="PATCH (HTTP)">PATCH</a></li></ul></td> </tr><tr><th class="sidebar-heading"> <a href="/wiki/List_of_HTTP_header_fields" title="List of HTTP header fields">Header fields</a></th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/HTTP_cookie" title="HTTP cookie">Cookie</a></li> <li><a href="/wiki/HTTP_ETag" title="HTTP ETag">ETag</a></li> <li><a href="/wiki/HTTP_location" title="HTTP location">Location</a></li> <li><a href="/wiki/HTTP_referer" title="HTTP referer">HTTP referer</a></li> <li><a href="/wiki/Do_Not_Track" title="Do Not Track">DNT</a></li> <li><a href="/wiki/X-Forwarded-For" title="X-Forwarded-For">X-Forwarded-For</a></li></ul></td> </tr><tr><th class="sidebar-heading"> <a href="/wiki/List_of_HTTP_status_codes" title="List of HTTP status codes">Response status codes</a></th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/HTTP_301" title="HTTP 301">301 Moved Permanently</a></li> <li><a href="/wiki/HTTP_302" title="HTTP 302">302 Found</a></li> <li><a href="/wiki/HTTP_303" title="HTTP 303">303 See Other</a></li> <li><a href="/wiki/HTTP_403" title="HTTP 403">403 Forbidden</a></li> <li><a href="/wiki/HTTP_404" title="HTTP 404">404 Not Found</a></li> <li><a href="/wiki/HTTP_451" title="HTTP 451">451 Unavailable for Legal Reasons</a></li></ul></td> </tr><tr><th class="sidebar-heading"> Security access control methods</th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Basic_access_authentication" title="Basic access authentication">Basic access authentication</a></li> <li><a href="/wiki/Digest_access_authentication" title="Digest access authentication">Digest access authentication</a></li></ul></td> </tr><tr><th class="sidebar-heading"> Security vulnerabilities</th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/HTTP_header_injection" title="HTTP header injection">HTTP header injection</a></li> <li><a class="mw-selflink selflink">HTTP request smuggling</a></li> <li><a href="/wiki/HTTP_response_splitting" title="HTTP response splitting">HTTP response splitting</a></li> <li><a href="/wiki/HTTP_parameter_pollution" title="HTTP parameter pollution">HTTP parameter pollution</a></li></ul></td> </tr><tr><td class="sidebar-navbar"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:HTTP" title="Template:HTTP"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:HTTP" title="Template talk:HTTP"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:HTTP" title="Special:EditPage/Template:HTTP"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <p><b>HTTP request smuggling</b> (<b>HRS</b>) is a <a href="/wiki/Security_exploit" class="mw-redirect" title="Security exploit">security exploit</a> on the <a href="/wiki/HTTP" title="HTTP">HTTP</a> protocol that takes advantage of an inconsistency between the interpretation of <a href="/wiki/List_of_HTTP_header_fields#content-length-response-header" title="List of HTTP header fields"><code>Content-Length</code></a> and <a href="/wiki/List_of_HTTP_header_fields#transfer-encoding-response-header" title="List of HTTP header fields"><code>Transfer-Encoding</code></a> headers between HTTP server implementations in an <a href="/wiki/HTTP_proxy_server" class="mw-redirect" title="HTTP proxy server">HTTP proxy server</a> chain.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-portswigger1_2-0" class="reference"><a href="#cite_note-portswigger1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> It was first documented in 2005 by Linhart et al.<sup id="cite_ref-HRS_3-0" class="reference"><a href="#cite_note-HRS-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>The Transfer-Encoding header works by defining a directive on how to interpret the body of the <a href="/wiki/HTTP_request" class="mw-redirect" title="HTTP request">HTTP request</a>, with the common and necessary directive for this attack being the <a href="/wiki/Chunked_transfer_encoding" title="Chunked transfer encoding">chunked transfer encoding</a>.<sup id="cite_ref-mozillatransfer_4-0" class="reference"><a href="#cite_note-mozillatransfer-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> When the Transfer-Encoding header is present, the Content-Length header is supposed to be omitted.<sup id="cite_ref-mozillatransfer_4-1" class="reference"><a href="#cite_note-mozillatransfer-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Working similarly but with a different syntax, the Content-Length header works by specifying the size in bytes of the body as a value in the header itself.<sup id="cite_ref-mozillacontentlength_5-0" class="reference"><a href="#cite_note-mozillacontentlength-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> Vulnerabilities arise when both of these headers are included in a malicious HTTP request, bypassing security functions meant to prevent malicious HTTP queries to the server by causing either the <a href="/wiki/Frontend_and_backend" title="Frontend and backend">front-end or back-end</a> server to incorrectly interpret the request.<sup id="cite_ref-imperva_6-0" class="reference"><a href="#cite_note-imperva-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> HTTP request smuggling commonly takes the form of CL.TE, TE.CL, or TE.TE, although more complex attacks using HRS do exist.<sup id="cite_ref-imperva_6-1" class="reference"><a href="#cite_note-imperva-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Types">Types</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=HTTP_request_smuggling&action=edit&section=1" title="Edit section: Types"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="CL.TE">CL.TE</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=HTTP_request_smuggling&action=edit&section=2" title="Edit section: CL.TE"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In this type of HTTP request smuggling, the front end processes the request using Content-Length header while backend processes the request using Transfer-Encoding header.<sup id="cite_ref-portswigger1_2-1" class="reference"><a href="#cite_note-portswigger1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> The attack would be carried out with the first part of the request declaring a zero length chunk.<sup id="cite_ref-imperva_6-2" class="reference"><a href="#cite_note-imperva-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> The front end server seeing this would only read the first part of the request and unintentionally pass the second part to the back end server.<sup id="cite_ref-imperva_6-3" class="reference"><a href="#cite_note-imperva-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Once passed through to the back end server, it would be treated as the next request and processed, carrying out the attackers hidden request.<sup id="cite_ref-imperva_6-4" class="reference"><a href="#cite_note-imperva-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="TE.CL">TE.CL</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=HTTP_request_smuggling&action=edit&section=3" title="Edit section: TE.CL"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In this type of HTTP request smuggling, the front end processes request using Transfer-Encoding header while backend processes the request using Content-Length header.<sup id="cite_ref-portswigger1_2-2" class="reference"><a href="#cite_note-portswigger1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> In this attack, a hacker would declare the valid length of the first chunk, which houses the malicious request and then declare a second chunk with a length of 0.<sup id="cite_ref-imperva_6-5" class="reference"><a href="#cite_note-imperva-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> When the front end server sees the second chunk with a length of 0 it believes the request to be complete and passes it along to the back end server.<sup id="cite_ref-imperva_6-6" class="reference"><a href="#cite_note-imperva-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> The back end server processes the request using the Content-Length header, however, and as a result the malicious request left in the first chunk go unprocessed until they are treating as being at the start of next request in the sequence and are carried out.<sup id="cite_ref-portswigger1_2-3" class="reference"><a href="#cite_note-portswigger1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="TE.TE">TE.TE</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=HTTP_request_smuggling&action=edit&section=4" title="Edit section: TE.TE"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In this type of HTTP request smuggling, the front end and backend both process the request using Transfer-Encoding header, but the header can be obfuscated in a way (for example by nonstandard whitespace formatting or duplicate headers) that makes one of the servers but not the other one ignore it.<sup id="cite_ref-portswigger1_2-4" class="reference"><a href="#cite_note-portswigger1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Obscuring the header may take the form of adding in an incorrect character, such as Transfer-Encoding: xchunked, or an unusual new line character between 'Transfer-Encoding' and ': chunked'.<sup id="cite_ref-imperva_6-7" class="reference"><a href="#cite_note-imperva-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> If one of the front of back end servers still processes these obfuscated HTTP requests, then the rest of the attack will be similar to how CL.TE or TE.CL attacks work.<sup id="cite_ref-imperva_6-8" class="reference"><a href="#cite_note-imperva-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Prevention">Prevention</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=HTTP_request_smuggling&action=edit&section=5" title="Edit section: Prevention"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The best prevention to these attacks would clearly be if front end and back end servers interpreted HTTP requests the same way. However, this is usually not an option as <a href="/wiki/Load_balancer" class="mw-redirect" title="Load balancer">load balancers</a> support backend servers run on distinct platforms, using different software.<sup id="cite_ref-imperva_6-9" class="reference"><a href="#cite_note-imperva-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Most variants<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources"><span title="Statement needs to be more specific about the content to which it refers. (May 2023)">specify</span></a></i>]</sup> of this attack can be prevented by using <a href="/wiki/HTTP/2" title="HTTP/2">HTTP/2</a>, as it uses a different method to determine the length of a request. Another method of avoiding the attack is for the frontend server to normalize HTTP requests before passing them to the backend, ensuring that they get interpreted in the same way.<sup id="cite_ref-portswigger1_2-5" class="reference"><a href="#cite_note-portswigger1-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Configuring a <a href="/wiki/Web_application_firewall" title="Web application firewall">web application firewall</a> is another good way to prevent HRS attacks as many feature technology that identify attack attempts and either blocks or sanitize the suspicious incoming requests.<sup id="cite_ref-imperva_6-10" class="reference"><a href="#cite_note-imperva-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>Grenfeldt et al. (2021) found that most front-end web servers (e.g. proxy servers) provided the parsing features for hindering in practice, all the known HRS attacks on the back-end web servers.<sup id="cite_ref-Grenfeldt_et_al._(2021)_7-0" class="reference"><a href="#cite_note-Grenfeldt_et_al._(2021)-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Huang et al. (2022) proposed a method using <a href="/wiki/Flask_(web_framework)" title="Flask (web framework)">Flask</a> so to implement suitable parsing features that prevent HRS attacks, from a front-end program or web server.<sup id="cite_ref-Huang_et_al._(2022)_8-0" class="reference"><a href="#cite_note-Huang_et_al._(2022)-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=HTTP_request_smuggling&action=edit&section=6" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://cwe.mitre.org/data/definitions/444.html">"CWE - CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') (4.0)"</a>. <i>cwe.mitre.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2020-03-13</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=cwe.mitre.org&rft.atitle=CWE+-+CWE-444%3A+Inconsistent+Interpretation+of+HTTP+Requests+%28%27HTTP+Request+Smuggling%27%29+%284.0%29&rft_id=https%3A%2F%2Fcwe.mitre.org%2Fdata%2Fdefinitions%2F444.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHTTP+request+smuggling" class="Z3988"></span></span> </li> <li id="cite_note-portswigger1-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-portswigger1_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-portswigger1_2-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-portswigger1_2-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-portswigger1_2-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-portswigger1_2-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-portswigger1_2-5"><sup><i><b>f</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://portswigger.net/web-security/request-smuggling">"What is HTTP request smuggling? Tutorial & Examples | Web Security Academy"</a>. <i>portswigger.net</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2020-03-13</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=portswigger.net&rft.atitle=What+is+HTTP+request+smuggling%3F+Tutorial+%26+Examples+%7C+Web+Security+Academy&rft_id=https%3A%2F%2Fportswigger.net%2Fweb-security%2Frequest-smuggling&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHTTP+request+smuggling" class="Z3988"></span></span> </li> <li id="cite_note-HRS-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-HRS_3-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLinhartKleinHeledOrrin2005" class="citation web cs1">Linhart, Chaim; Klein, Amit; Heled, Ronen; Orrin, Steve (2005). <a rel="nofollow" class="external text" href="https://www.cgisecurity.com/lib/HTTP-Request-Smuggling.pdf">"HTTP request smuggling"</a> <span class="cs1-format">(PDF)</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=HTTP+request+smuggling&rft.date=2005&rft.aulast=Linhart&rft.aufirst=Chaim&rft.au=Klein%2C+Amit&rft.au=Heled%2C+Ronen&rft.au=Orrin%2C+Steve&rft_id=https%3A%2F%2Fwww.cgisecurity.com%2Flib%2FHTTP-Request-Smuggling.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHTTP+request+smuggling" class="Z3988"></span></span> </li> <li id="cite_note-mozillatransfer-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-mozillatransfer_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-mozillatransfer_4-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Transfer-Encoding">"Transfer-Encoding"</a>. <i>developer.mozilla.org</i><span class="reference-accessdate">. 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