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Advisory record · GHSA-4m7w-qmgq-4wj5

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

CVSS 2.7 LowEPSS 0.0047 · 41st percentile

Published by the GitHub Advisory Database at 15 Jun 2026, 20:11 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
aiohttpPyPI<3.14.13.14.1
Identifiers
GHSA-4m7w-qmgq-4wj5 · CVE-2026-54275 · PYSEC-2026-237
Weakness (CWE)
CWE-297
Tags
Published
15 Jun 2026
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The aiohttp package, versions before 3.14.1, can reuse an existing HTTPS connection for a request that specifies a different server_hostname, so the TLS hostname check is skipped and the request may succeed when it should have been rejected. The source does not describe what an attacker must control to exploit this. Upgrade to aiohttp 3.14.1. If you cannot upgrade, disable keep-alive for requests that need a different server_hostname.

Written 4 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
2.7 Low 4.0 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 CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0047, the 41st percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 8 Jun 2026, 20:11 UTC Published by the maintainers as a GitHub repository advisory
  2. 31 Oct 2026, 14:29 UTC First seen by agentprime
  3. 31 Oct 2026, 14:29 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.