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of outdated or incompatible HTTP protocol versions in the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.
-
Implementation
Terminate the client session after each request.
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System Configuration
Turn all pages to non-cacheable.
Source: MITRE CWE-444
170 results · Clear filters · Feed
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Medium 4.8
In JetBrains Ktor before 3.6.1 hTTP request smuggling was possible in the CIO engine
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Medium 5.3
Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 HTTP Response Splitting via wasi-http
Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 contains a response splitting vulnerability in wasi-http p3 that allows guests to set unvalidated content-length headers. Malicious wasip3 guests can splice an existing body into a new response with an in…
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Medium 6.9
uhttpd vulnerable to HTTP request smuggling via case-sensitive Transfer-Encoding matching
uhttpd is a small HTTP server. In unpatched repository snapshots, `client_parse_header()` in `client.c` lowercases header names but compares the `Transfer-Encoding` value to `chunked` using case-sensitive `strcmp`. A mixed-case transfer-coding token is accept…
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Medium 6.9
uhttpd: HTTP request smuggling via ubus POST body parse-error desync
uhttpd is a small HTTP server. In unpatched repository snapshots, `uh_ubus_data_send()` in `ubus.c` can desynchronize HTTP request boundaries when a `POST /ubus` JSON body arrives in multiple TCP segments. An initial segment completing a JSON object sets `du-…
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Medium 6.5
Undertow: undertow: chunkreader message length permits chunk-size overflow
A flaw was found in the ChunkReader component of the Undertow web server, which is used to handle chunked transfer encoding in HTTP requests. The issue occurs because a security check for the chunk size is performed before the value is shifted, allowing a spe…
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Medium 6.3
Chunk extensions accept bare LF and CR, enabling request smuggling in Bandit
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in the HTTP/1.1 chunked body reader of mtrudel bandit allows an unauthenticated remote attacker to smuggle a second request past a front-end proxy via a chunk exten…
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Medium 5.4
Twisted: HTTP Request Smuggling in twisted.web via a Bare CR or LF in a Header Value
Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 26.10.0rc1, twisted.web.http.HTTPChannel.headerReceived rejects a NUL byte in an HTTP header value but accepts a bare carriage return or bare line feed. Because Tw…
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Medium 6.9
NetX Duo Web HTTP server interprets request body content as HTTP header fields
The Web add-on's HTTP server searches the entire request packet for header fields instead of stopping at the end of the header section. A header field name placed in the request body is therefore reported to the server as though it were a header, which lets a…
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Medium 6.3
Pingora HTTP/2 :authority and Host header mismatch enables cache poisoning and host-based access control bypass
Summary Before version 0.9.0, Pingora accepted HTTP/2 requests whose Host header differed from the :authority pseudo-header. Request filters, cache keys, and logs that read the request URI (session.req_header().uri) saw the :authority value, but the upstream …
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Medium 6.3
AIOHTTP: Pure-Python parser request smuggling
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, the pure Python parser accepts ambiguous HTTP request framing. An unauthenticated attacker can consequently smuggle requests when an application uses AIOHTTP_NO_E…
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Medium 6.3
HTTP Request Smuggling Vulnerability in Progress® Telerik® Fiddler® Classic
In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, HTTP request smuggling is possible in the proxy request forwarding component. Requests containing multiple Content-Length headers with conflicting values are forwarded ver…
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Medium 5.3
Libsoup: soupserver: http/1 request smuggling via undrained expect: 100-continue body
A flaw was found in SoupServer (libsoup). When an HTTP/1.x client sends a request with Expect: 100-continue and a request body, and SoupServer returns an early final (non-1xx) response before the body is read, the server neither drains the declared body bytes…
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Medium 6.3
Mint HTTP/1 client applies chunked framing when chunked is not the final transfer coding, enabling response smuggling through intermediaries
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in elixir-mint mint allows a malicious HTTP/1 server to desynchronize an intermediary and the Mint client on a pooled connection, poisoning the responses to subsequ…
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Medium 5.4
http4k before 6.49.0.0 Host Header Routing Bypass via reverseProxy
http4k (Maven package org.http4k:http4k-core) before 6.49.0.0, 5.42.0.0 and 4.51.0.0 uses substring (Contains) matching on the Host header by default in reverseProxy() and reverseProxyRouting() when dispatching to configured virtual hosts. If these functions …
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Medium 6.5
Netty 4.2.0 through 4.2.17 HTTP/3 Request Routing Bypass
Netty's HTTP/3 codec (io.netty:netty-codec-http3) in versions 4.2.0.Final through 4.2.17.Final does not enforce the RFC 9114 requirement that the :authority pseudo-header field and a literal host header field, when both present, carry the same value. A remote…
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Medium 6.3
Unvalidated chunk-size line tail in Mint HTTP/1 client enables response smuggling against strict intermediaries on pooled connections
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in elixir-mint mint allows a malicious HTTP/1 server to desynchronize a strict intermediary and the Mint client on a pooled connection, enabling response-queue pois…
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Medium 6.5
Io.netty/netty-codec-http: netty: http request smuggling via post-digit whitespace in chunk-size parsing
A flaw was found in Netty's `netty-codec-http` component. A remote attacker could exploit this vulnerability by sending a specially crafted HTTP/1.1 chunk-size token that includes post-digit whitespace. This incorrect parsing of the chunk size can lead to HTT…
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Medium 4.8
IBM WebSphere Application Server and IBM WebSphere Application Server - Liberty HTTP Request Smuggling
IBM WebSphere Application Server 8.5 and 9.0, and IBM WebSphere Application Server - Liberty 17.0.0.3 through 26.0.0.8 are affected by an HTTP request smuggling vulnerability.
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Medium 6.5
IBM WebSphere Application Server is affected by an HTTP request smuggling vulnerability
IBM WebSphere Application Server 8.5 is affected by an HTTP request smuggling vulnerability due to improper handling of Content-Length headers.
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Medium 4.8
IBM WebSphere Application Server and IBM WebSphere Application Server - Liberty HTTP Request Smuggling
IBM WebSphere Application Server 8.5 and 9.0, and and IBM WebSphere Application Server - Liberty 17.0.0.3 through 26.0.0.8 are affected by an HTTP request smuggling vulnerability.
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Medium 4.8
IBM WebSphere Application Server and IBM WebSphere Application Server - Liberty HTTP Request Smuggling
IBM WebSphere Application Server 8.5 and 9.0, and IBM WebSphere Application Server - Liberty 17.0.0.3 through 26.0.0.8 are vulnerable to HTTP request smuggling.
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Medium 6.5
Io.netty/netty-codec-http: netty split transfer-encoding fields bypass final-chunked validation and enable request smuggling
A flaw was found in Netty's HTTP/1.1 decoder. This vulnerability allows a remote attacker to bypass `Transfer-Encoding` header validation by splitting the `Transfer-Encoding` field across multiple headers, with the last field containing a non-final transfer c…
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Medium 6.5
Breeze Cache 1.2.5 - 2.5.14 - Unauthenticated Cache Poisoning via Unkeyed Tracking Parameters
The Breeze Cache WordPress plugin before 2.5.15 does not include a set of tracking-related query parameters in its page-cache key while still caching pages requested with them, allowing unauthenticated attackers to have a page rendered under their own request…
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Medium 6.5
sanic chunked trailer request smuggling allows hidden second request execution
Sanic is an opensource python web server/framework. In version 25.12.0, Sanic's core HTTP/1.1 chunked-body handling does not fully consume the trailer-part after the terminating zero chunk before reusing the keep-alive connection buffer. A remote unauthentica…
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Medium 5.4
Http4s: Ember chunk parser lenience (TE.TE request smuggling)
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s chunk decoder trims the chunk-size token and accepts leading plus or minus signs instead of requiring one or more hexadecimal digits followed by the required CRLF. When an …
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Medium 6.5
IBM WebSphere Application Server IBM WebSphere Application Server - Liberty HTTP Request Smuggling
IBM WebSphere Application Server 8.5 and 9.0, and IBM WebSphere Application Server - Liberty 17.0.0.3 through 26.0.0.8 are vulnerable to HTTP request smuggling, caused by improper parsing of the HTTP transfer-encoding request header. By sending a specially cr…
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Medium 6.5
IBM WebSphere Application Server and IBM WebSphere Application Server - Liberty Request Smuggling
IBM WebSphere Application Server 8.5 and 9.0, and IBM WebSphere Application Server - Liberty 17.0.0.3 through 26.0.0.8 are vulnerable to HTTP request smuggling, caused by improper parsing of the HTTP transfer-encoding request header. By sending a specially cr…
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Medium 6.5
Netty 4.1.133.Final through 4.1.137.Final and 4.2.13.Final through 4.2.17.Final HTTP Request Smuggling via Transfer-Encoding
Netty versions 4.1.133.Final through 4.1.137.Final and 4.2.13.Final through 4.2.17.Final fail to properly validate the final transfer coding in the Transfer-Encoding header, allowing attackers to smuggle requests by using malformed encoding declarations. Atta…
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Medium 5.6CVE-2026-84380 Public exploit
HTTPX2: Conflicting Content-Length and Transfer-Encoding headers can be auto-generated
HTTPX2 is a next generation HTTP client for Python. Prior to 2.11.0, Request._prepare() in src/httpx2/httpx2/_models.py can add a body-derived Content-Length header to a request that already contains a caller-supplied Transfer-Encoding header because its setd…
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Medium 5.9
Hono: Query parser reads parameters after the URL fragment, causing cache-key and proxy interpretation differentials
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.13.5, Hono's query helpers treat a question mark after a literal hash fragment as the start of a query string, so the application can read request parameters that…
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Medium 5.9
Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') in Elasticsearch Leading to Information Disclosure
Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') (CWE-444) in Elasticsearch can lead to information disclosure via HTTP Request Smuggling (CAPEC-33). Under specific proxy deployment configurations, a network attacker could obtain confid…
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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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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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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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Medium 6.1
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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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…