CVE-2026-128128AIOHTTP: WebSocket max_msg_size bypass via integer overflow

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, the C WebSocket reader adds a declared frame length to the size of an already buffered partial message using signed 64-bit arithmetic. A length near two to the power of 63 can overflow, allowing the max_msg_size check to pass. A remote peer can send a small non-final fragment followed by an oversized message and cause unbounded memory consumption. The Python WebSocket reader is unaffected. This issue is fixed in version 3.14.4.

Data: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Published as the sources state it, in English.

Affected products and versions

References and patches

• https://github.com/aio-libs/aiohttp/security/advisories/GHSA-3rp8-rxj8-mvjw
• https://github.com/aio-libs/aiohttp/pull/13415
• https://github.com/aio-libs/aiohttp/pull/13494
• https://github.com/aio-libs/aiohttp/commit/8c8906a19f64e52ef6a7d44d65217eb3c5af413f
• https://github.com/aio-libs/aiohttp/commit/8cfbe9abe5e11b84006a10f9bdf82bf607671dab
• https://github.com/aio-libs/aiohttp/releases/tag/v3.14.4