CVE-2026-84379: Pydantic HTTPX2

Medium severity, CVSS 5.3. EPSS: 0.3% chance of exploitation in the next 30 days.

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 products

• Pydantic HTTPX2: before 2.11.0 (fixed in 2.11.0)

Published 2026-09-02. Last modified 2026-09-09.