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Algorithmic Complexity Affecting python-httpx2 package, versions <2.12.0-1

Severity

 Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.32% (23rd percentile)

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  • Snyk IDSNYK-DEBIANUNSTABLE-PYTHONHTTPX2-19502074
  • published3 Sept 2026
  • disclosed2 Sept 2026
Report a new vulnerability Found a mistake?

Introduced: 2 Sep 2026

CVE-2026-84378  (opens in a new tab)
CWE-407  (opens in a new tab)

How to fix?

Upgrade Debian:unstable python-httpx2 to version 2.12.0-1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream python-httpx2 package and not the python-httpx2 package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

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.