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CVE-2026-84378 Details

Description

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.

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:5.9 MEDIUMVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/pydantic/httpx2/commit/cbfc0e04ef6507da29ccbb3b9c2e5b23dd693414	[email protected]
https://github.com/pydantic/httpx2/pull/1071	[email protected]
https://github.com/pydantic/httpx2/pull/1117	[email protected]
https://github.com/pydantic/httpx2/releases/tag/v2.10.0	[email protected]
https://github.com/pydantic/httpx2/security/advisories/GHSA-f2fp-rgf2-35cp	[email protected]

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-407	Inefficient Algorithmic Complexity	[email protected]

Affected Products

No affected product data is available for this CVE.

Change History

2 change records found show changes

Date	Action	Recorded By
Sep 2, 2026	CVE Modified	CISA-ADP
Sep 2, 2026	New CVE Received	[email protected]