aiohttp: TLS Server Hostname Override Is Ignored When Reusing HTTPS Connections

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2026-54275: 0.47% estimated exploitation activity in the next 30 days; percentile 40.74 (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 The serverhostname TLS SNI check can be bypassed when an existing connection is reused. Impact If an application makes multiple requests to the same domain, but with different per-request serverhostname parameters, then the later calls may succeed by reusing the existing connection when they should have been rejected due to the TLS SNI check. Workaround Disable keepalive if you need to change the serverhostname check between requests. ----- Patch: https://github.com/aio-libs/aiohttp/commit/0ca2b6c28a25726527a8b60f25960262a91ed0e0

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-4m7w-qmgq-4wj5

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-4m7w-qmgq-4wj5

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# Patch Next advisory brief: CVE-2026-54275

Advisory: aiohttp: TLS Server Hostname Override Is Ignored When Reusing HTTPS Connections
IDs: CVE-2026-54275, GHSA-4m7w-qmgq-4wj5
Record: https://patchnext.com/advisories/cve-2026-54275 (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: Low (CVSS 2.7)
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-4m7w-qmgq-4wj5 (OSV record GHSA-4m7w-qmgq-4wj5 lists affected ranges: PyPI aiohttp >=0 <3.14.1 (fixed))
- Verified: https://github.com/advisories/GHSA-4m7w-qmgq-4wj5 (GitHub-reviewed advisory GHSA-4m7w-qmgq-4wj5 lists affected ranges: PyPI aiohttp >=0 <=3.14.0)

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