CVE-2026-84378
mediumHTTPX2 is a next generation HTTP client for Python.
HTTPX2 is a next generation HTTP client for Python. From 2.5.0 until 2.10.0, the HTTPX2 Server-Sent Events parser in src/httpx2/httpx2/_sse.py repeatedly copies and rescans buffered text in _SSELineDecoder.decode() when an attacker-controlled or compromised SSE endpoint splits one unterminated line across many response chunks. The behavior affects httpx2.Client.sse() and httpx2.AsyncClient.sse(), and the total processing work grows quadratically with the line length, allowing a crafted stream to consume excessive CPU and block a synchronous worker or asynchronous event loop. This issue is fixed in version 2.10.0.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H Affected products
Not reported by the source (unknown — not "none").
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
No vendor advisory or patch reference tagged by NVD. Check the references below.
References
- https://github.com/pydantic/httpx2/commit/cbfc0e04ef6507da29ccbb3b9c2e5b23dd693414 security-advisories@github.com
- https://github.com/pydantic/httpx2/pull/1071 security-advisories@github.com
- https://github.com/pydantic/httpx2/pull/1117 security-advisories@github.com
- https://github.com/pydantic/httpx2/releases/tag/v2.10.0 security-advisories@github.com
- https://github.com/pydantic/httpx2/security/advisories/GHSA-f2fp-rgf2-35cp security-advisories@github.com