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of outdated or incompatible HTTP protocol versions in the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)
-
Implementation
Use a web server that employs a strict HTTP parsing procedure, such as Apache [REF-433].
-
Implementation
Use only SSL communication.
-
Implementation
Terminate the client session after each request.
-
System Configuration
Turn all pages to non-cacheable.
Source: MITRE CWE-444
406 results · Feed
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Low 3.7
A flaw in Node.js HTTP client can cause a request desynchronization for Node.js-based forwarding proxies that rebuild o…
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Medium 6.5CVE-2026-51376 Public exploit
An issue in BitChat for iOS v1.15.0 allows a remote attacker to cause a denial of service via an unauthenticated MESSAG…
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High 7.0
Apache APISIX: Cross-user response poisoning in serverless plugins
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in Apache APISIX. An attacker could make other clients receive attacker-chosen or other users' responses on serverless-plugin routes. This issue affects Apache APIS…
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Medium 5.3
Reverse::Proxy versions before 0.04 for Perl allow HTTP request smuggling via a percent-decoded PATH_INFO written unencoded to the upstream request line
Reverse::Proxy versions before 0.04 for Perl allow HTTP request smuggling via a percent-decoded PATH_INFO written unencoded to the upstream request line. PSGI hands PATH_INFO to an application percent-decoded, so a %XX sequence in the client URL has become a …
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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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Medium 6.3
Libevent: HTTP Header smuggling
Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent processes chunked HTTP trailers in http.c through evhttp_read_trailer and merges them into request headers. The fix introduces evhttp_parse_headers_impl_ and a temporary trai…
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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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Medium 6.1CVE-2026-55087 Scanner template
Etherpad: x-proxy-path header reflected into admin HTML/JS/CSS (cache-poisoning XSS) and concatenated into redirect (open-redirect)
Etherpad is a real-time collaborative editor. From 2.1.0 until 3.1.0, Etherpad uses the attacker-controlled x-proxy-path request header in src/node/hooks/express/admin.ts when substituting paths into HTML, JavaScript, and CSS under /admin without sanitization…
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Medium 6.3
actix-http before 3.12.1 HTTP Request Smuggling via CL.TE
actix-http versions before 3.12.1 contain an HTTP request smuggling vulnerability in the HTTP/1.1 parser that accepts requests with both Content-Length and Transfer-Encoding: chunked headers. Unauthenticated remote attackers can exploit this through a front-e…
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High 7.4
blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)
blaze is a Scala library for building asynchronous pipelines, with a focus on network IO. Prior to 0.23.18 and 1.0.0-M42, blaze-server can merge HTTP/1.1 chunked-body trailer fields into Request.headers. Because trailer fields are attacker-controlled, an unau…
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High 7.5
ServiceTalk HTTP/1.x incorrectly handles malformed Transfer-Encoding which could result in request smuggling attacks. T…
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Medium 5.9
.NET Security Feature Bypass Vulnerability
Inconsistent interpretation of http requests ('http request/response smuggling') in .NET allows an unauthorized attacker to bypass a security feature over a network.
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Medium 5.3
Undertow-core: undertow:http request smuggling via oversized chunk-size bit overlap
A flaw was found in the ChunkReader component of the Undertow HTTP server, which is used by WildFly and JBoss EAP to handle chunked transfer encoding. The issue occurs because the parser uses a single internal variable to store both the remaining chunk size a…
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Medium 6.1
Instatic - Cache Poisoning via Unauthenticated Server Island Endpoint
A cache poisoning vulnerability in CoreBunch/Instatic through 0.0.14 allows an unauthenticated remote attacker to poison the shared process-wide render cache by manipulating the u query parameter of the GET /_instatic/hole/<nodeId> server island endpoint.
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Medium 5.3CVE-2026-71554 Public exploit
h2: Duplicate Host header could facilitate request smuggling
h2 is a pure-Python implementation of a HTTP/2 protocol stack. Versions up to and including 4.4.0 accept request header blocks containing more than one Host header, and forward every Host header to the consuming application. Where the consumer downgrades HTTP…
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High 7.0
Traefik: Cross-user response poisoning via proxied CONNECT on Traefik's shared backend keep-alive pool
Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.53, 3.6.24, and 3.7.9, Traefik's default HTTP reverse proxy forwards a plain HTTP/2 or HTTP/3 CONNECT request and its body to an HTTP/1.1 upstream through a shared net/http.Transpor…
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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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Low 3.7CVE-2026-58044 Public exploit
A flaw in Node.js HTTP client can cause a request desynchronization for Node.js-based forwarding proxies that rebuild o…
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Medium 6.3CVE-2026-69243 Public exploit
AIOHTTP: HTTP request smuggling via WebSocket upgrade
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.2, the HTTP parsers were vulnerable to a request smuggling attack relating to WebSocket upgrades. If using the server-side component, an attacker may be able to exec…
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Medium 5.6
HTTP Smuggling in cPanel allows potential leak of credentials.
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Medium 4.8
undici vulnerable to downstream response desynchronization via retry interceptor
undici's retry interceptor can deliver a response whose body length does not match the Content-Length header exposed to the application after a retry or resume of a partial response. In undici before 6.28.0, from 7.0.0 up to before 7.29.0, and from 8.0.0 up t…
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Medium 6.3
Netty: WebSockets V07/V08 handshaker missing Connection/Upgrade validation
Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, ab attacker can force WebSocket upgrade via the lax V07 (or V08) handshaker by sending `Sec-WebSocket-Version: 7` and omitting `Connection:…
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Medium 6.9
Netty codec-http2: Lack of Host Header Deduplication in HTTP/2→HTTP/1.x Translation Leads to Request Routing Bypass
Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, Netty's HTTP/2-to-HTTP/1.x translation layer (`Http2StreamFrameToHttpObjectCodec` and `InboundHttp2ToHttpAdapter`) fails to deduplicate or …
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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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High 8.3
Apache Traffic Server: HTTP/2 to HTTP/1 conversion forwards origin trailers to clients unsafely
Apache Traffic Server forwards HTTP/2 origin trailers to HTTP/1 clients without proper chunked framing when converting HTTP/2 to HTTP/1. This issue affects Apache Traffic Server: from 10.0.0 through 10.1.3. Users are recommended to upgrade to version 9.2.15 o…
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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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High 7.2
Apache Traffic Server: Request smuggling via chunked extension quoted-string parsing
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in Apache Traffic Server. This issue affects Apache Traffic Server: from 10.0.0 through 10.1.3, from 9.0.0 through 9.2.14. Users are recommended to upgrade to versi…
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High 8.7
IBM WebSphere Application Server and WebSphere Application Server Liberty are affected by multiple vulnerabilities
IBM WebSphere Application Server and IBM WebSphere Application Server - Liberty is vulnerable to HTTP Response Smuggling due to improper handling of non-standard HTTP version tokens.
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High 8.7
IBM WebSphere Application Server and WebSphere Application Server Liberty are affected by multiple vulnerabilities
IBM WebSphere Application Server and IBM WebSphere Application Server - Liberty is vulnerable to HTTP request smuggling due to improper handling of TRACE requests.
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High 7.4
IBM WebSphere Application Server and WebSphere Application Server Liberty is inconsistent Interpretation of HTTP Requests
IBM WebSphere Application Server and IBM WebSphere Application Server - Liberty is vulnerable to HTTP request smuggling.
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High 7.5CVE-2026-67182 Public exploit
Rouille 0.3.3 - 3.6.2 HTTP Request Smuggling via proxy Header Injection
Rouille 0.3.3 through 3.6.2 contains an HTTP request smuggling vulnerability that allows remote attackers to bypass access controls by injecting bare line feed characters (0x0A) into client-supplied request header values that are copied verbatim to upstream c…
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Medium 5.4CVE-2026-67181 Public exploit
Rouille 0.3.3 - 3.6.2 HTTP Request Smuggling via proxy Transfer-Encoding Header
Rouille 0.3.3 through 3.6.2 contains an HTTP request smuggling vulnerability that allows remote attackers to desynchronize HTTP message boundaries by exploiting improper header forwarding in the proxy implementation. The proxy in src/proxy.rs forwards the cli…
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Medium 5.4CVE-2026-66752 Public exploit
tiny-http 0.12.0 HTTP Request Smuggling via Transfer-Encoding Handling
tiny-http through 0.12.0 contains an HTTP request smuggling vulnerability that allows remote attackers to desynchronize request framing by sending a Transfer-Encoding header with any value, including non-chunked codings, which causes the library to unconditio…
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Medium 5.4
Libsoup: libsoup: http request smuggling via permissive chunk-size parsing in soup_body_input_stream_read_chunked()
A flaw was found in libsoup. The chunked transfer encoding parser uses a permissive parsing function for chunk sizes that silently accepts inputs violating RFC 9112, including leading whitespace, plus sign prefixes, and trailing invalid characters. When libso…
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Medium 5.3
swift-nio-http2: Missing CR/LF/NUL validation in header values
SwiftNIO HTTP/2 was missing validation on inbound HEADERS frames that let CR, LF, NUL, SP and other control characters reach an HTTP/1.1 backend through NIOHTTP2's HTTP/2-to-HTTP/1 codec, enabling HTTP request smuggling or response splitting. This vulnerabili…
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High 7.8
Skipper: opaAuthorizeRequestWithBody filter bypasses OPA policy on Transfer-Encoding: chunked / HTTP/2 requests
Skipper is an HTTP router and reverse proxy for service composition. Prior to 0.26.10, zalando/skipper's OpenPolicyAgent integration silently bypasses request-body inspection on HTTP/1.1 Transfer-Encoding: chunked and HTTP/2 requests that omit the content-len…
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Medium 6.3
Sign-tolerant HTTP/1 chunk-size parser in Mint enables response smuggling against strict intermediaries on pooled connections
Inconsistent interpretation of HTTP requests (HTTP response smuggling) vulnerability in elixir-mint mint allows a malicious HTTP/1 server to desynchronize a strict intermediary and the Mint client on the same pooled connection, enabling response-queue poisoni…