What’s Vulnerable › Vulnerabilities

CVE-2026-63349: AnyIO run_process/open_process ignores extra_groups and can retain parent supplementary groups

• Severity: high (CVSS 7.0 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-18 · updated 2026-09-25
• Weakness: CWE-266

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.

Affected products

• agronholm anyio: from 4.14.0, < 4.14.2

References

• https://github.com/agronholm/anyio/commit/eb562e6462ee46b1904e50b02ce00a858cdeb200
• https://github.com/agronholm/anyio/pull/1209
• https://github.com/agronholm/anyio/releases/tag/4.14.2
• https://github.com/agronholm/anyio/security/advisories/GHSA-3w57-8xmc-8v26

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