Vulnerability · Published Sep 18, 2026 · Assigned by GitHub_M

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

High 7.0

In plain English

A high-severity privilege mismanagement in anyio from agronholm. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 1% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)7.0High

Exploit odds (30 days)0.1%top 98.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	python-anyio	no fix listed	DEBIAN-CVE-2026-63349
Debian:13	python-anyio	no fix listed	DEBIAN-CVE-2026-63349
Debian:14	python-anyio	4.15.1-1	DEBIAN-CVE-2026-63349
PyPI	anyio	4.14.2	GHSA-3w57-8xmc-8v26
PyPI	anyio	4.14.2	PYSEC-2026-4023
Ubuntu:22.04:LTS	python-anyio	no fix listed	UBUNTU-CVE-2026-63349
Ubuntu:24.04:LTS	python-anyio	no fix listed	UBUNTU-CVE-2026-63349
Ubuntu:26.04:LTS	python-anyio	no fix listed	UBUNTU-CVE-2026-63349
Ubuntu:26.10	python-anyio	no fix listed	UBUNTU-CVE-2026-63349

Affected products (as reported)

Vendor	Product	Versions
agronholm	anyio	>= 4.14.0, < 4.14.2

Weakness: CWE-266, CWE-269 · 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

References

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