Vulnerability · Published Sep 2, 2026 · Assigned by GitHub_M
CVE-2026-84379HTTPX2: Multipart part header injection via unvalidated file Content-Type and custom headers
Medium 5.3
In plain English
A medium-severity security flaw in httpx2 from pydantic. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 25% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
HTTPX2 is a next generation HTTP client for Python. Prior to 2.11.0, FileField.render_headers() in src/httpx2/httpx2/_multipart.py directly interpolates attacker-controlled content_type values and custom headers from the files= three-element (filename, content, content_type) tuple and the files= four-element (filename, content, content_type, headers) tuple into multipart/form-data part headers without validating header names or values. CR or LF characters can terminate a part header, inject additional part headers, or end the part header block early, allowing a downstream multipart parser to treat attacker-supplied lines as genuine headers and potentially alter part semantics or bypass header-based checks. This issue is fixed in version 2.11.0.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:14 | python-httpx2 | 2.12.0-1 | DEBIAN-CVE-2026-84379 |
| PyPI | httpx2 | 2.11.0 | GHSA-h4x7-gw46-3wm6 |
| PyPI | httpx2 | 2.11.0 | PYSEC-2026-3848 |
| Ubuntu:26.10 | python-httpx2 | no fix listed | UBUNTU-CVE-2026-84379 |
Affected products (as reported)
Weakness: CWE-93 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
References
- https://github.com/pydantic/httpx2/security/advisories/GHSA-h4x7-gw46-3wm6 x_refsource_CONFIRM
- https://github.com/pydantic/httpx2/pull/1142 x_refsource_MISC
- https://github.com/pydantic/httpx2/commit/de96d810ee4e309d118982fe7084a46a2bcd600d x_refsource_MISC
- https://github.com/pydantic/httpx2/releases/tag/v2.11.0 x_refsource_MISC