CVE-2026-59881: AIOHTTP: WebSocket client accepts compressed frames without negotiated permessage-deflate

August 3, 2026

The client accepts and decompresses frames with the RSV1 bit set even when the permessage-deflate extension was not negotiated.

References

github.com/advisories/GHSA-mq44-7p77-q5h7
github.com/aio-libs/aiohttp/commit/47fb6ae354d4fa22048f4dbe7dbf82b625f0a2f6
github.com/aio-libs/aiohttp/pull/12978
github.com/aio-libs/aiohttp/security/advisories/GHSA-mq44-7p77-q5h7
nvd.nist.gov/vuln/detail/CVE-2026-59881

Code Behaviors & Features

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