CVE-2026-128128

HIGH 7.5

AIOHTTP: WebSocket max_msg_size bypass via integer overflow

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-770
Vendor	aio-libs
Product	aiohttp
Published	Nov 13, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Affected Versions

aio-libs / aiohttp

< 3.14.4

References

NVD ↗ CVE.org ↗ EPSS Data ↗

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