HTTP Request Smuggling Affecting httpx2 package, versions [,2.11.0)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published1 Oct 2026
- disclosed8 Sept 2026
- creditUnknown
Introduced: 8 Sep 2026
NewCVE-2026-84380 (opens in a new tab)How to fix?
Upgrade httpx2 to version 2.11.0 or higher.
Overview
httpx2 is a The next generation HTTP client.
Affected versions of this package are vulnerable to HTTP Request Smuggling in Request._prepare(), which applies a generated Content-Length header through setdefault() whenever the body size is known, without checking whether the caller has already supplied a Transfer-Encoding header, so both mutually exclusive framing headers can appear on one HTTP/1.1 request. An attacker can smuggle a request or desynchronize a persistent connection, reaching other requests sharing it, bypassing front end routing or authorization decisions, and poisoning responses or caches, by getting a Transfer-Encoding header and matching body data into a request the application constructs. This requires HTTP/1.1, an application that forwards attacker influenced framing headers into the request, and an intermediary or origin that accepts the conflicting pair rather than rejecting the message outright.