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PYSEC-2026-3547
AIOHTTP: WebSocket client accepts compressed frames without negotiated permessage-deflate
Quick fix
PYSEC-2026-3547 — aiohttp: upgrade to the fixed version with the command below.
pip install --upgrade 'aiohttp>=3.14.2'Details
### Summary
The client accepts and decompresses frames with the RSV1 bit set even when the `permessage-deflate` extension was not negotiated.
### Impact
A client may unexpectedly decompress WebSocket frames when explicitly opted out. This could lead to additional CPU/memory consumption, but is unlikely to be a significant issue unless a zip bomb vulnerability or similar is also present.
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Patch: https://github.com/aio-libs/aiohttp/commit/47fb6ae354d4fa22048f4dbe7dbf82b625f0a2f6
Are you affected?
Enter the version of the package you're using.
Affected packages
References
- https://github.com/aio-libs/aiohttp/security/advisories/GHSA-mq44-7p77-q5h7[WEB]
- https://nvd.nist.gov/vuln/detail/CVE-2026-59881[ADVISORY]
- https://github.com/aio-libs/aiohttp/pull/12978[WEB]
- https://github.com/aio-libs/aiohttp/commit/47fb6ae354d4fa22048f4dbe7dbf82b625f0a2f6[WEB]
- https://github.com/aio-libs/aiohttp[PACKAGE]
- http://github.com/aio-libs/aiohttp/releases/tag/v3.14.2[WEB]
- https://pypi.org/project/aiohttp[PACKAGE]
- https://github.com/advisories/GHSA-mq44-7p77-q5h7[ADVISORY]