CVSS 3.1
5.9 mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HCVE-2026-84378
Medium (5.9). EPSS 0.3% chance of exploitation in the next 30 days. Fixed in httpx2 2.10.0.
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.
Severity
- EPSS
- 0.3% chance of exploitation in the next 30 days; higher than 24% of CVEs (scores of 2026-10-31)
- CWE
- CWE-407
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-f2fp-rgf2-35cp | PyPI | httpx2 | >=2.5.0 <2.10.0 | 2.10.0 |
| PYSEC-2026-3847 | PyPI | httpx2 | >=2.5.0 <2.10.0 | 2.10.0 |