CVE-2026-63349

AnyIO run_process/open_process ignores extra_groups and can retain parent supplementary groups

Published Sep 18, 2026 CVSS 4.0 · 7 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-3w57-8xmc-8v26 AnyIO run_process/open_process ignores extra_groups and can retain parent supplementary groups
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Weaknesses CWE-648
References
Metrics threat_severity

None

cvssV3_1

{'score': 4.4, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N'}

threat_severity

Moderate

Type Values Removed Values Added
First Time appeared Agronholm
Agronholm anyio
Vendors & Products Agronholm
Agronholm anyio
Type Values Removed Values Added
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.
Title AnyIO run_process/open_process ignores extra_groups and can retain parent supplementary groups
Weaknesses CWE-266
CWE-269
References
Metrics cvssV4_0

{'score': 7, 'vector': 'CVSS:4.0/AV:L/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Sep 24, 2026, 9:05 PM
Reserved
Jul 16, 2026, 2:14 PM
Status
Awaiting Analysis
Published
Sep 18, 2026, 5:16 PM
Modified
Sep 25, 2026, 2:10 PM
Severity
Moderate
Public date
Sep 18, 2026, 5:02 PM