Weakness (CWE)
CWE-444: Inconsistent Interpretation of HTTP Requests
The product acts as an intermediary HTTP agent
(such as a proxy or firewall) in the data flow between two
entities such as a client and server, but it does not
interpret malformed HTTP requests or responses in ways that
are consistent with how the messages will be processed by
those entities that are at the ultimate destination.
More detail
HTTP requests or responses ("messages") can be
malformed or unexpected in ways that cause web servers or
clients to interpret the messages in different ways than
intermediary HTTP agents such as load balancers, reverse
proxies, web caching proxies, application firewalls,
etc. For example, an adversary may be able to add duplicate
or different header fields that a client or server might
interpret as one set of messages, whereas the intermediary
might interpret the same sequence of bytes as a different
set of messages. For example, discrepancies can arise in
how to handle duplicate headers like two Transfer-encoding
(TE) or two Content-length (CL), or the malicious HTTP
message will have different headers for TE and
CL.
The inconsistent parsing and interpretation of messages
can allow the adversary to "smuggle" a message to the
client/server without the intermediary being aware of it.
This weakness is usually the result of the usage
of outdated or incompatible HTTP protocol versions in the
HTTP agents.
How to prevent it (4 mitigations)
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Implementation
Use a web server that employs a strict HTTP parsing procedure, such as Apache [REF-433].
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Implementation
Use only SSL communication.
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Implementation
Terminate the client session after each request.
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System Configuration
Turn all pages to non-cacheable.
Source: MITRE CWE-444
73 results · Clear filters · Feed
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Critical 9.1
Starlet versions before 0.33 for Perl send a body in responses to HEAD requests, corrupting the next response on a persistent or pipelined connection
Starlet versions before 0.33 for Perl send a body in responses to HEAD requests, corrupting the next response on a persistent or pipelined connection. The request method is not passed to the response writer, so whatever body the application returns for a HEAD…
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Critical 9.1
Echo: Rejected WebSocket upgrades can bypass Echo route-level access controls
Echo is a Go web framework. From 4.0.0 until 4.16.1 and 5.4.1, Echo's Proxy middleware selects a raw tunnel from a client WebSocket upgrade request before verifying that the configured upstream accepted the upgrade. If the upstream rejects the upgrade with an…
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Critical 9.1
Starman versions before 0.4019 for Perl send response bodies for HEAD requests, desynchronizing responses on keep-alive connections
Starman versions before 0.4019 for Perl send response bodies for HEAD requests, desynchronizing responses on keep-alive connections. For a HEAD request Starman omits chunked framing but still writes the body returned by the application, on both the array and …
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Critical 9.3
Apache Traffic Server: HEAD requests carrying Content-Length or Transfer-Encoding enable request smuggling
Apache Traffic Server allows request smuggling via HEAD requests that carry Content-Length or Transfer-Encoding. This issue affects Apache Traffic Server: from 8.0.0 through 8.1.11, from 9.0.0 through 9.2.15, from 10.0.0 through 10.1.4, 10.2.0. Users are reco…
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Critical 9.3
Apache Traffic Server: A malformed 302 response bypasses parse-error rejection through the Transfer-Encoding: chunked carve-out
Apache Traffic Server forwarded a malformed 302 response that should have been rejected as a parse error, because the Transfer-Encoding: chunked carve-out bypassed the rejection path. A response that two peers can read differently is then stored and served, a…
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Critical 9.4
ASP.NET Core Tampering Vulnerability
Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an unauthorized attacker to perform tampering over a network.
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Critical 9.1
ASP.NET Core Security Feature Bypass Vulnerability
Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an unauthorized attacker to bypass a security feature over a network.
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Critical 9.3CVE-2026-88773 Public exploit
HTTP Request Smuggling
Inconsistent interpretation of HTTP requests ('HTTP Request/Response smuggling') vulnerability in Citrix NetScaler ADC and Citrix NetScaler Gateway. This issue affects ADC: before 14.1-73.37, before 13.1-64.23, before 14.1-73.37 FIPS, and before 13.1-37.279 a…
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Critical 9.1CVE-2026-86350 Public exploit
Apache Tomcat: Regression in fix for CVE-2026-41293 can trigger request header mix-up
Inconsistent interpretation of HTTP/2 requests ('HTTP Request/Response smuggling') vulnerability in Apache Tomcat caused by a regression in fix for CVE-2026-41293 can trigger request header mix-up. This issue affects Apache Tomcat: from 11.0.22 through 11.0.2…
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Critical 9.8
Ambiguous parsing of mail headers
A maliciously constructed mail header could lead to multiple fields being parsed as one, or potential memory safety violations. This vulnerability was fixed in Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.
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Critical 9.2
Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/1.1 does not reject messages containing both Transfer-Encoding and Content-Length, so an intermediary and Ember can select different body framing rules. When ember-serve…
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Critical 9.1
An issue in Puma v.5.0.0 and before v.8.0.3 allows an attacker to execute arbitrary code via the ext/puma_http11/http11…
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Critical 9.2
Libevent: HTTP header handling bugs create risk of access control bypass.
Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has two HTTP parsing weaknesses in http.c. evhttp_decode_uri_internal decodes percent-encoded %00 bytes into literal NUL characters, which can cause downstream C string opera…
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Critical 9.2
libevent evhttp: Multiple HTTP Parser Bugs Enable Request Smuggling
Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, the libevent evhttp parser in http.c inconsistently handles duplicate Transfer-Encoding headers, comma-separated Transfer-Encoding values, and bare line feeds in chunked framing. evht…
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Critical 9.1
Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE
Mongoose is an embedded web server and network library. Prior to 7.22, a remote unauthenticated attacker can exploit an HTTP/1.0 reverse-proxy deployment by sending a request with Transfer-Encoding: chunked and conflicting framing. The http_cb() function in s…
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Critical 9.1
Mongoose: Content-Length + Transfer-Encoding coexistence enables request smuggling
Mongoose is an embedded web server and network library. Priro to version 7.22, a remote unauthenticated attacker can send an HTTP request containing both Content-Length and Transfer-Encoding: chunked. The cl_count and te_count checks in the mg_http_parse() an…
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Critical 9.1
HTTP request smuggling in Progress MarkLogic Server
An HTTP request smuggling vulnerability in the HTTP App Server of Progress MarkLogic Server before 11.3.6 and 12.0.3 allows a remote attacker to bypass authentication and authorization checks, hijack a legitimate user's session, or capture credentials. The vu…
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Critical 9.3
Apache Traffic Server: Header-name length truncation enables header aliasing and request smuggling
Apache Traffic Server truncates over-long header names, allowing header aliasing, request smuggling, and policy bypass. This issue affects Apache Traffic Server: from 8.0.0 through 8.1.11, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3. Users are recom…
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Critical 10.0
Apache Traffic Server: HTTP/2 requests with Transfer-Encoding are not rejected, allowing request smuggling
Apache Traffic Server does not reject Transfer-Encoding in HTTP/2 requests, allowing downgrade request smuggling. This issue affects Apache Traffic Server: from 8.0.0 through 8.1.11, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3. Users are recommended…
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Critical 10.0
Apache Traffic Server: Malformed chunked message body allows request smuggling
Apache Traffic Server allows request smuggling if chunked messages are malformed. This issue affects Apache Traffic Server: from 8.0.0 through 8.1.11, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3. Users are recommended to upgrade to version 9.2.15 or…
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Critical 9.1
HTTP Request Smuggling in SAP Approuter
Due to an HTTP Request Smuggling vulnerability in SAP Approuter, an unauthenticated attacker could send a specially crafted HTTP request that leads to request-response desynchronization. This could result in the exposure of user responses and cause the system…
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Critical 9.8
HTTP/2 Stream Parser Confusion Body-Inspection Bypass in AWS Application Load Balancer with AWS WAF
Inconsistent interpretation of HTTP/2 requests in AWS Application Load Balancer with AWS WAF enabled might allow remote actors to bypass AWS WAF managed rule body inspection via crafted HTTP/2 requests that fragment the request body across frames so that only…
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Critical 9.8
HTTP/2 Stream Parser Confusion Body-Inspection Bypass in Amazon CloudFront with AWS WAF
Inconsistent interpretation of HTTP/2 requests in Amazon CloudFront with AWS WAF enabled might allow remote actors to bypass AWS WAF managed rule body inspection via crafted HTTP/2 requests that fragment the request body across frames so that only a partial b…
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Critical 9.1
vLLM: OpenAI auth bypass
vLLM is an inference and serving engine for large language models (LLMs). From 0.3.0 until 0.22.0, a vulnerability in ASGI web servers and starlette's trust on those web servers enables an authentication bypass of the OpenAI API AuthenticationMiddleware. It a…
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Critical 9.1
Tinyproxy - HTTP Request Smuggling via Duplicate Content-Length Headers
Tinyproxy through 1.11.3, fixed in commit 364cdb6, fails to reject requests containing multiple Content-Length headers with differing values, forwarding all duplicate headers to the backend while using the first value to determine how many request body bytes …
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Critical 9.1
Tinyproxy - HTTP Request Smuggling via CL/TE Desynchronization
Tinyproxy through 1.11.3, fixed in commit ff45d3b, fails to reconcile conflicting Content-Length and Transfer-Encoding: chunked headers, forwarding both verbatim to the backend while using Content-Length to determine how many request body bytes to consume. Re…
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Critical 9.9
cpp-httplib: HTTP header value percent-decoding in server-side `parse_header` enables CRLF injection
cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, when cpp-httplib's server parses an incoming request, it applies percent-decoding to every header value except Location and Referer. The validity check (is_fiel…
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Critical 9.8
Pony Mail: Admin account takeover via request smuggling
** UNSUPPORTED WHEN ASSIGNED ** Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in Pony Mail leading to admin account takeover. This issue affects all versions of the Lua implementation of Pony Mail. There is a P…
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Critical 9.0
@fastify/reply-from vulnerable to connection header abuse enabling stripping of proxy-added headers
@fastify/reply-from v12.6.1 and earlier and @fastify/http-proxy v11.4.3 and earlier process the client's Connection header after the proxy has added its own headers via rewriteRequestHeaders. This allows attackers to retroactively strip proxy-added headers fr…
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Critical 9.8
Mitigation bypass in the Networking: HTTP component
Mitigation bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
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Critical 9.3
TinyWeb: Integer Overflow in `_Val` (HTTP Request Smuggling)
TinyWeb is a web server (HTTP, HTTPS) written in Delphi for Win32. Prior to version 2.03, an integer overflow vulnerability in the string-to-integer conversion routine (_Val) allows an unauthenticated remote attacker to bypass Content-Length restrictions and …
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Critical 9.3CVE-2026-2835 Public exploit
HTTP Request Smuggling via HTTP/1.0 and Transfer-Encoding Misparsing
An HTTP Request Smuggling vulnerability (CWE-444) has been found in Pingora's parsing of HTTP/1.0 and Transfer-Encoding requests. The issue occurs due to improperly allowing HTTP/1.0 request bodies to be close-delimited and incorrect handling of multiple Tran…
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Critical 9.3
HTTP Request Smuggling via Premature Upgrade
An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on t…
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Critical 9.9
ASP.NET Security Feature Bypass Vulnerability
Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an authorized attacker to bypass a security feature over a network.
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Critical 9.8CVE-2025-56266 Scanner template
A Host Header Injection vulnerability in Avigilon ACM v7.10.0.20 allows attackers to execute arbitrary code via supplyi…
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Critical 9.1
Radware Cloud Web Application Firewall (WAF) before 2025-05-07 allows remote attackers to bypass firewall filters by pl…
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Critical 9.1
h11 accepts some malformed Chunked-Encoding bodies
h11 is a Python implementation of HTTP/1.1. Prior to version 0.16.0, a leniency in h11's parsing of line terminators in chunked-coding message bodies can lead to request smuggling vulnerabilities under certain conditions. This issue has been patched in versio…
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Critical 9.1
croogo Host header injection
An issue in croogo v.3.0.2 allows an attacker to perform Host header injection via the feed.rss component.
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Critical 9.1
Request smuggling due to acceptance of invalid chunked data in net/http
The net/http package improperly accepts a bare LF as a line terminator in chunked data chunk-size lines. This can permit request smuggling if a net/http server is used in conjunction with a server that incorrectly accepts a bare LF as part of a chunk-ext.
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Critical 10.0
HTTP Response Smuggling Vulnerability in libhv
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in ithewei libhv allows HTTP Response Smuggling.This issue affects libhv: through 1.3.3.