aiohttp: Incomplete websocket frame payloads bypass memory limits

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.6 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U · score source

EPSS

• CVE-2026-54274: 0.54% estimated exploitation activity in the next 30 days; percentile 45.43 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary If an attacker sends large incomplete websocket frame payloads, it may be possible to bypass the usual size limits on memory use. Impact If a web application has WebSocket endpoints, it may be possible for an attacker to execute a DoS attack through excessive memory use. ----- Patch: https://github.com/aio-libs/aiohttp/commit/14b6ee851fb16ec199acb950de0c82d476799e7d

Published by the source

15 Jun 2026, 20:11 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 13:45 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-xcgm-r5h9-7989

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-xcgm-r5h9-7989

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# Patch Next advisory brief: CVE-2026-54274

Advisory: aiohttp: Incomplete websocket frame payloads bypass memory limits
IDs: CVE-2026-54274, GHSA-xcgm-r5h9-7989
Record: https://patchnext.com/advisories/cve-2026-54274 (revision 3, source checked 26 Oct 2026, 13:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: aiohttp 3.14.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI aiohttp: affected <= 3.14.0; fixed in 3.14.1

## Suggested inspection (read-only)
- `python -m pip show aiohttp`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on aiohttp.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-xcgm-r5h9-7989 (OSV record GHSA-xcgm-r5h9-7989 lists affected ranges: PyPI aiohttp >=0 <3.14.1 (fixed))
- Verified: https://github.com/advisories/GHSA-xcgm-r5h9-7989 (GitHub-reviewed advisory GHSA-xcgm-r5h9-7989 lists affected ranges: PyPI aiohttp >=0 <=3.14.0)

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