CWE-444Base4 in KEV

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

Incomplete in the CWE catalog · 258 CVEs mapped

258
CVEs mapped
4
In KEV
6.8
Median CVSS
What it is

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.

Recent examples
3.7cvss
CVE-2026-18540

CVE-2026-18540 - LOW Severity Vulnerability

undici's retry interceptor can append the body of a ranged retry response to bytes already delivered from an earlier partial response while still presenting the original response's status and headers. This happens when an upstream server delivers part of a body without a trustworthy resume checkpoint, for example a non-success response whose headers were already sent or a partial-content response with an unusable content range, then closes the connection and answers the resumed range request with more bytes. As a result the response body can be longer than the Content-Length that the application observes. An application that relays such a response to a downstream HTTP/1.1 peer without normalizing the framing can emit a body that exceeds the forwarded Content-Length, and the excess bytes can be interpreted as the start of a following response, which enables downstream response splitting or desynchronization. Exploitation requires an attacker-controlled upstream server and an application that forwards the response through a framing-sensitive path. This affects undici versions before 6.28.1, from 7.0.0 up to 7.29.1, and from 8.0.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.

LOWno explanation yet
0%
epss
5.6cvss
CVE-2026-84380

CVE-2026-84380 - MEDIUM Severity Vulnerability

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 setdefault() processing checks each default header independently rather than treating the two framing headers as mutually exclusive. Fixed-size byte, JSON, form, and known-length multipart bodies can therefore be serialized over HTTP/1.1 with both headers, allowing request smuggling or connection desynchronization when downstream intermediaries disagree about which framing header takes precedence. This issue is fixed in version 2.11.0.

MEDIUMno explanation yet
0%
epss
5.9cvss
CVE-2026-84363

CVE-2026-84363 - MEDIUM Severity Vulnerability

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 browsers, new URL(), reverse proxies, filtering rules, parameter allow and deny lists, access logging, request validation, and other middleware do not observe. The Cache Middleware removes the fragment when building its cache key, allowing a response influenced by parameters inside the fragment to be stored under a key that omits those parameters and later served to other users. This can bypass filtering and auditing, poison cached responses, and enable stored cross-site scripting when an affected parameter is reflected into cached HTML without escaping. Exploitation requires a runtime and intermediary path that passes a literal hash character through to the request URL; Cloudflare Workers and intermediaries that strip fragments are not affected. This issue is fixed in version 4.13.5.

MEDIUMno explanation yet
0%
epss
The record
Technical detail
CWE ID
CWE-444
Abstraction
Base
Structure
Simple
Status
Incomplete
References (7)