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Advisory record · GHSA-5p39-cfhj-2xmp

AnyIO process-pool workers can block indefinitely on undrained stderr

CVSS 6.8 MediumEPSS 0.0016 · 4th percentile

Published by the GitHub Advisory Database at 18 Sept 2026, 17:17 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
anyioPyPI<4.14.24.14.2
Identifiers
GHSA-5p39-cfhj-2xmp · CVE-2026-64847 · PYSEC-2026-4024
Weakness (CWE)
CWE-770
Tags
Published
18 Sept 2026
Updated
1 Oct 2026

Machine-written summary

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

AnyIO versions before 4.14.2 are affected. Process-pool workers do not redirect stderr, so worker code that writes enough data to stderr can fill the pipe and block the awaiting process-pool call indefinitely. The source gives few details on who can trigger this beyond running untrusted or faulty code. Upgrade to anyio 4.14.2, which contains the fix.

Written 1 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
6.8 Medium 4.0 CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0016, the 4th percentile, on 13 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:09 UTC First seen by agentprime
  2. 31 Oct 2026, 14:09 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.