GHSA-f2fp-rgf2-35cp: httpx2 (CVE-2026-84378)

Package	Ecosystem	Affected	Fixed in
httpx2	PyPI	>=2.5.0, <2.10.0	2.10.0

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

HTTPX2 versions from 2.5.0 before 2.10.0 are vulnerable to quadratic processing in the Server-Sent Events parser when a server sends one long line split across many small chunks. An attacker who controls or compromises an SSE endpoint that the client consumes can make the client use excessive CPU, which can block a synchronous worker or the async event loop and degrade availability. Upgrade to httpx2 2.10.0 or later; until then, consume SSE only from trusted endpoints and enforce an external size or time limit on the stream.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
5.9	Medium	3.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0032, the 24th percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:10 UTC First seen by agentprime
31 Oct 2026, 14:10 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.