CVE-2026-64847: Agronholm Anyio

Medium severity, CVSS 6.8. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Agronholm Anyio: before 4.14.2 (fixed in 4.14.2)

Published 2026-09-18. Last modified 2026-09-24.