23 Oct 2026 15:48:27 UTC
AnyIO process-pool workers can block indefinitely on undrained stderr
cve-program · CVE-2026-64847 · Published
CVE-2026-64847
AnyIO process-pool workers can block indefinitely on undrained stderr
CVSS 4.0 6.8 MEDIUMCheck source for fixed versionsKEV status unknown
cve-program · CVE-2026-64847
PublishedAnyIO 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.
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