CVE-2026-64847

CVE-2026-64847 · AnyIO process-pool workers can block indefinitely on undrained stderr

This page contains facts from public vulnerability sources. Check the original advisory before updating.

AnyIO is a high level asynchronous concurrency and networking framework that works on top of either Trio or asyncio. Prior to 4.14.2, AnyIO starts process-pool workers with standard error connected to a pipe that the parent never drains, even though the documented behavior redirects all three standard streams. Worker code that writes enough attacker-influenced data to sys.stderr can fill the pipe and block before returning the standard-output protocol response, causing the awaiting process-pool call to remain blocked indefinitely. Applications that run untrusted or faulty worker code capable of producing substantial standard-error output are affected. This issue is fixed in version 4.14.2.

CVSS 6.8 · Medium · EPSS 0.2% · Fix available

Published

2026-09-18T17:04:32.038Z

Updated

2026-09-18T18:07:27.772Z

Stack: system · python

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