CVE-2026-84380
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.
Scoring
- Severity
- MEDIUM
- CVSS base score
- 5.6
- CVSS vector
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
- EPSS probability
- 0.22%
- CWE
- CWE-444
- Published
- 2026-09-02
- Last modified
- 2026-09-02
Affected products
- pydantic httpx2
Weakness type
Related vulnerabilities
- CVE-2026-81356 — Visual Studio Code Security Feature Bypass Vulnerability
- CVE-2026-19203 — A client may issue specially crafted HTTP/1.1 chunked requests to a Jetty server that cause Jetty...
- CVE-2026-18540 — undici vulnerable to downstream response splitting via retry interceptor
- CVE-2026-84363 — Hono: Query parser reads parameters after the URL fragment, causing cache-key and proxy interpretation differentials
- CVE-2026-78605 — Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') in Elasticsearch Leading to Information Disclosure
- CVE-2026-73812 — inets, httpd: HTTP Request Smuggling via Transfer-Encoding and Content-Length
- CVE-2026-73276 — inets, httpd: HTTP Request Smuggling via Whitespace-Before-Colon Header Dropping i
- CVE-2026-66357 — inets,httpd:HTTP Request Smuggling via obs-fold Header Continuation