# CVE-2026-128129: AIOHTTP: Unbounded buffering of data received during an upgrade request

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, aiohttp buffers all additional connection data received while a request marked for upgrade, such as a WebSocket handshake, is being handled, without a size limit or flow control. A remote attacker can stream data behind an upgrade request to a handler that does not immediately accept or reject the upgrade and cause unbounded memory consumption. This issue is fixed in version 3.14.4.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- aio-libs / aiohttp: < 3.14.4 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 4.0: 8.2 (high); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-770

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/aio-libs/aiohttp/security/advisories/GHSA-pw86-h8fm-j323 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/aio-libs/aiohttp/pull/13501 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/aio-libs/aiohttp/pull/13511 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/aio-libs/aiohttp/commit/3d850ee9b92573c7e913821cbcb96005beb3f4df (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/aio-libs/aiohttp/commit/c207cadb257e0959b192ffca0548eca8c71eb96a (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/aio-libs/aiohttp/releases/tag/v3.14.4 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-128129; retrieved 2026-11-13; source updated 2026-11-13

Revision: 25d7e27494f95685fc777e3f36303b5f6f282c12c49216efb286d2a769a1ddb0

Canonical: https://y2.dev/cve/CVE-2026-128129

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