Quick answers
- Is CVE-2026-64847 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-64847 being exploited in the wild.
- How severe is CVE-2026-64847?
- Medium severity, with a CVSS score of 4, published 18 September 2026.
- Which products and versions are affected?
- anyio (PyPI) < 4.14.2, ECOSYSTEM:introduced=0,fixed=4.14.2.
- Is there a fix for CVE-2026-64847?
- Yes. anyio (PyPI): upgrade to 4.14.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-64847 attacked?
- It is attacked with local access, in a software library.
- Am I affected by CVE-2026-64847?
- Check whether you run anyio (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- anyio (PyPI): upgrade to 4.14.2 or later
pip install "anyio>=4.14.2"
Technical details
The vulnerability is a resource exhaustion issue (CWE-770) in AnyIO's process-pool worker initialization. AnyIO redirects stdin and stdout to /dev/null for protocol protection but fails to drain the stderr pipe despite documentation claiming all three standard streams are redirected. When untrusted code or a malicious actor writes sufficient data to stderr, the pipe buffer fills completely, causing the worker to block on subsequent stderr writes before it can return the stdout protocol response. This blocks the awaiting process-pool call indefinitely. Exploitation requires the ability to execute code in the process pool (low privilege requirement, local attack vector). The fix is available in version 4.14.2.
Affected products
- agronholm AnyIO < 4.14.2
Identifiers
- CVE-2026-64847
- GHSA-5p39-cfhj-2xmp
- PYSEC-2026-4024
Timeline
- 2026-07-07: disclosed
- 2026-09-18: advisory
- 2026-09-18: patched: Version 4.14.2 released