Summary
AnyIO runprocess/openprocess ignores extra_groups and can retain parent supplementary groups
AnyIO 4.14.0 accepts the POSIX extra_groups argument on anyio.run_process() and anyio.open_process(), but open_process() forwards the wrong variable to the backend: when extra_groups is not None, it assigns kwargs["extra_groups"] = group instead of extra_groups. As a result, callers cannot reliably clear or set supplementary groups for child processes. In a disposable Linux container, Python's subprocess.run(..., extra_groups=[]) clears a synthetic parent supplementary group list, while anyio.run_process(..., extra_groups=[]) preserves the parent groups. If group is also supplied, AnyIO passes an integer as extra_groups and the call fails with TypeError. This is a POSIX privilege-dropping correctness issue for applications that rely on AnyIO subprocess helpers to launch less-privileged child processes.
Impact
The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access. Typical impact: privilege escalation beyond the intended level.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Frequently Asked Questions
- What is CVE-2026-63349? CVE-2026-63349 is a high-severity improper privilege management vulnerability in anyio (pip), affecting versions >= 4.14.0, < 4.14.2. It is fixed in 4.14.2. The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access.
- Which versions of anyio are affected by CVE-2026-63349? anyio (pip) versions >= 4.14.0, < 4.14.2 is affected.
- Is there a fix for CVE-2026-63349? Yes. CVE-2026-63349 is fixed in 4.14.2. Upgrade to this version or later.
- Is CVE-2026-63349 exploitable, and should I be worried? Whether CVE-2026-63349 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-63349 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-63349? Upgrade
anyioto 4.14.2 or later.