Common Weakness Enumeration

CWE-444

Allowed

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

Abstraction: Base · Status: Incomplete

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.

699 vulnerabilities reference this CWE, most recent first.

CVE-2026-73256 (GCVE-0-2026-73256)

Vulnerability from cvelistv5 – Published: 2026-08-20 17:37 – Updated: 2026-08-21 21:46
VLAI
Title
Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE
Summary
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 src/http.c tests hm.proto.len with an impossible greater-than-eight condition even though mg_http_parse() requires an eight-byte protocol string, so is_http_1_0 is never set. Mongoose consequently processes chunked encoding that an HTTP/1.0 proxy can ignore, enabling request smuggling and unauthorized access or state changes. This issue is fixed in version 7.22.
SSVC
Exploitation: none Automatable: yes Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-21 21:10 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Impacted products
Vendor Product Version
cesanta mongoose Affected: < 7.22
Create a notification for this product.
Show details on NVD website

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CVE-2026-73051 (GCVE-0-2026-73051)

Vulnerability from cvelistv5 – Published: 2026-08-14 11:35 – Updated: 2026-08-14 13:58
VLAI
Title
actix-http before 3.12.1 HTTP Request Smuggling via CL.TE
Summary
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-end intermediary to desynchronize backend requests and smuggle malicious HTTP requests to the Actix service.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-14 13:58 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
References
Impacted products
Vendor Product Version
actix actix-web Affected: 0 , < 3.12.0 (semver)
Unaffected: 3.12.0 (semver)
    cpe:2.3:a:actix:actix-web:*:*:*:*:*:rust:*:*
Create a notification for this product.
Date Public
2026-04-18 00:00
Credits
Show details on NVD website

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CVE-2026-72587 (GCVE-0-2026-72587)

Vulnerability from cvelistv5 – Published: 2026-08-10 10:41 – Updated: 2026-08-10 13:21
VLAI
Title
Instatic - Cache Poisoning via Unauthenticated Server Island Endpoint
Summary
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.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-10 13:21 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
References
URL Tags
https://github.com/CoreBunch/Instatic third-party-advisory
Impacted products
Vendor Product Version
CoreBunch Instatic Affected: 0 , ≤ 0.0.14 (semver)
Create a notification for this product.
Date Public
2026-08-10 10:32
Show details on NVD website

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CVE-2026-71554 (GCVE-0-2026-71554)

Vulnerability from cvelistv5 – Published: 2026-08-06 21:46 – Updated: 2026-08-08 02:49
VLAI
Title
h2: Duplicate Host header could facilitate request smuggling
Summary
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/2 to HTTP/1.1, the resulting request carries two Host header lines, providing a request smuggling primitive. This issue is fixed in version 4.4.1.
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-08 02:49 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
References
Impacted products
Vendor Product Version
python-hyper h2 Affected: < 4.4.1
Create a notification for this product.
Show details on NVD website

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CVE-2026-71324 (GCVE-0-2026-71324)

Vulnerability from cvelistv5 – Published: 2026-08-06 15:56 – Updated: 2026-08-07 15:43
VLAI
Title
Traefik: Cross-user response poisoning via proxied CONNECT on Traefik's shared backend keep-alive pool
Summary
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.Transport. When the upstream answers the CONNECT with a keep-alive non-2xx response and does not drain the body, Traefik returns the desynchronized backend socket to its shared pool and reuses it for other clients. An unauthenticated attacker can use this behavior to make a different client read the attacker's smuggled response, which can include authenticated or private content from another request. The ForwardAuth middleware with forwardBody true and preserveRequestMethod true can re-issue a CONNECT with the buffered body attached, exposing the auth-client pool to the same desynchronization. This issue is fixed in 2.11.53, 3.6.24, and 3.7.9.
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-07 15:43 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Impacted products
Vendor Product Version
traefik traefik Affected: < 2.11.53
Affected: >= 3.0.0, < 3.6.24
Affected: >= 3.7.0, < 3.7.9
Create a notification for this product.
Show details on NVD website

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CVE-2026-69243 (GCVE-0-2026-69243)

Vulnerability from cvelistv5 – Published: 2026-08-03 20:45 – Updated: 2026-08-05 14:54
VLAI
Title
AIOHTTP: HTTP request smuggling via WebSocket upgrade
Summary
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 execute a request smuggling vulnerability using an edge case in the WebSocket upgrade procedure. A WebSocket upgrade request with a body could cause the parser to switch protocols before the complete request body was received, leaving trailing bytes to be handled as upgraded-protocol or pipelined data rather than normal HTTP body data. This issue is fixed in version 3.14.2.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-05 14:53 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Impacted products
Vendor Product Version
aio-libs aiohttp Affected: < 3.14.2
Create a notification for this product.
Show details on NVD website

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CVE-2026-69217 (GCVE-0-2026-69217)

Vulnerability from cvelistv5 – Published: 2026-09-15 19:20 – Updated: 2026-09-16 13:52
VLAI
Title
Http4s: Ember Server accepts duplicate Content-Length headers
Summary
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HTTP/1.1 parser accepts differing duplicate Content-Length headers and uses the last value instead of rejecting the message. When an Ember server is behind a keep-alive intermediary that selects a different occurrence, an unauthenticated attacker can create CL.CL request smuggling that bypasses front-end controls, captures a later user’s headers, or poisons a cache. The shared client parser can also misframe responses from a malicious or compromised upstream when the client acts as a proxy for multiple downstream consumers. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-16 13:52 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Impacted products
Vendor Product Version
http4s http4s Affected: < 0.23.35
Affected: >= 1.0.0-M1, < 1.0.0-M47
Create a notification for this product.
Show details on NVD website

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CVE-2026-69216 (GCVE-0-2026-69216)

Vulnerability from cvelistv5 – Published: 2026-09-15 18:59 – Updated: 2026-09-16 13:53
VLAI
Title
Http4s: Ember chunk parser lenience (TE.TE request smuggling)
Summary
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 intermediary forwards chunked data without re-encoding and interprets malformed chunk boundaries differently, an unauthenticated attacker can create TE.TE request smuggling that bypasses intermediary controls, poisons caches, or hijacks the request queue. The same response-path leniency can enable response smuggling against an ember-client used as a gateway when the upstream is malicious or compromised. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-16 13:53 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Impacted products
Vendor Product Version
http4s http4s Affected: < 0.23.35
Affected: >= 1.0.0-M1, < 1.0.0-M47
Create a notification for this product.
Show details on NVD website

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CVE-2026-69205 (GCVE-0-2026-69205)

Vulnerability from cvelistv5 – Published: 2026-09-15 19:15 – Updated: 2026-09-15 19:33
VLAI
Title
Http4s: Ember Transfer-Encoding value parsing (TE.CL / TE.0 request smuggling)
Summary
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HeaderP.parse uses a case-sensitive substring test for the Transfer-Encoding value and decodes header bytes with the platform default charset. Values such as Chunked are not recognized, values such as notchunked are incorrectly accepted, and Unicode case folding can turn a Kelvin-sign byte sequence into a match when UTF-8 is used. Intermediaries that apply RFC-compliant token and charset rules can therefore disagree with Ember’s Content-Length or zero-length framing, enabling TE.CL or TE.0 request smuggling, access-control bypass, cross-user request hijacking, and cache poisoning on the server path. Response smuggling through an ember-client gateway requires a malicious or compromised upstream. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-15 19:32 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Impacted products
Vendor Product Version
http4s http4s Affected: < 0.23.35
Affected: >= 1.0.0-M1, < 1.0.0-M47
Create a notification for this product.
Show details on NVD website

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CVE-2026-69204 (GCVE-0-2026-69204)

Vulnerability from cvelistv5 – Published: 2026-09-15 18:43 – Updated: 2026-09-15 19:00
VLAI
Title
Http4s: Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling)
Summary
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-server is behind a keep-alive intermediary that forwards both headers and frames by Content-Length, an unauthenticated attacker can smuggle a second request, bypass intermediary access controls, poison caches, or cause a victim request to be joined to an attacker-controlled prefix. The shared response parser can also desynchronize an ember-client connection when a malicious or compromised upstream sends both headers. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-15 19:00 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Impacted products
Vendor Product Version
http4s http4s Affected: < 0.23.35
Affected: >= 1.0.0-M1, < 1.0.0-M47
Create a notification for this product.
Show details on NVD website

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Mitigation
Implementation

Use a web server that employs a strict HTTP parsing procedure, such as Apache [REF-433].

Mitigation
Implementation

Use only SSL communication.

Mitigation
Implementation

Terminate the client session after each request.

Mitigation
System Configuration

Turn all pages to non-cacheable.

CAPEC-273: HTTP Response Smuggling

An adversary manipulates and injects malicious content in the form of secret unauthorized HTTP responses, into a single HTTP response from a vulnerable or compromised back-end HTTP agent (e.g., server).

See CanPrecede relationships for possible consequences.

CAPEC-33: HTTP Request Smuggling

An adversary abuses the flexibility and discrepancies in the parsing and interpretation of HTTP Request messages using various HTTP headers, request-line and body parameters as well as message sizes (denoted by the end of message signaled by a given HTTP header) by different intermediary HTTP agents (e.g., load balancer, reverse proxy, web caching proxies, application firewalls, etc.) to secretly send unauthorized and malicious HTTP requests to a back-end HTTP agent (e.g., web server).

See CanPrecede relationships for possible consequences.