CVE-2026-63349: agronholm anyio Incorrect Privilege Assignment

Vulnerability summary

CVE-2026-63349 is a high (CVSS 7.0) Incorrect Privilege Assignment vulnerability in agronholm anyio. EPSS estimates a 0.11% chance of exploitation in the next 30 days, higher than 1.1% of scored vulnerabilities.

Timeline

1. 18-09-2026
   PublishedVulnerability first disclosed.
2. 24-09-2026
   Last modifiedVulnerability information updated.

Description

AnyIO is a high level asynchronous concurrency and networking framework that works on top of either Trio or asyncio. In 4.14.0, AnyIO accepts the POSIX extra_groups argument in anyio.run_process() and anyio.open_process(), but open_process() forwards the group argument to the backend instead of extra_groups. A caller that supplies extra_groups=[] to clear inherited supplementary groups can therefore launch a child that retains the parent process groups, undermining a privilege-dropping boundary. If group is also supplied, the integer group value is passed where an iterable of supplementary groups is expected and the launch can fail with TypeError. This issue affects POSIX applications that rely on AnyIO subprocess helpers to launch less-privileged child processes. This issue is fixed in version 4.14.2.

• CWE-266Incorrect Privilege AssignmentA product incorrectly assigns a privilege to a particular actor, creating an unintended sphere of control for that actor.
• CWE-269Improper Privilege ManagementThe product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.