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

> AnyIO subprocess helpers ignore extra_groups, allowing child processes to retain parent supplementary groups and bypass privilege dropping.

- **Severity:** High 7.0 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Sep 2026
- **Updated:** 24 Sep 2026
- **Also known as:** CLEANSTART-2026-KA42623, DEBIAN-CVE-2026-63349, ECHO-5d39-da23-651e, GHSA-3w57-8xmc-8v26, MINI-29w7-xvw9-ccfj, MINI-2r7c-pm44-m9v2, MINI-3hvx-37q5-96x3, MINI-77c9-3c9j-p6q3, MINI-84gc-r8cg-mc44, MINI-8pwr-6hfr-xmmh, MINI-cmxr-gqxq-6rfg, MINI-gf26-xv38-g8wc, MINI-jqf7-xcfv-8phx, MINI-ppg9-q73v-8858, MINI-prc6-9685-q292, MINI-pwq8-p39c-mjh7, MINI-r9vr-2885-7944, MINI-w5jf-q9fq-cwxv, MINI-wqc2-9jq7-pp35, MINI-x3ph-8xc2-49wx, PYSEC-2026-4023, ROOT-APP-PYPI-CVE-2026-63349, UBUNTU-CVE-2026-63349

## What is CVE-2026-63349?

CVE-2026-63349 is a high-severity vulnerability in agronholm anyio, published on 18 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### 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.

Weakness: CWE-269 (Improper Privilege Management), CWE-266 (Incorrect Privilege Assignment)

## Which versions are affected by CVE-2026-63349?

3 open source packages ship an affected version, including anyio.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `anyio` | PyPI | From 4.14.0 | 4.14.2 |
| `anyio` | PyPI | From 4.14.0 | 4.14.2 |
| `anyio` | PyPI | From 4.14.0 | 4.14.2 |

## How do I fix CVE-2026-63349?

Upgrade anyio to 4.14.2 or later.

## Is CVE-2026-63349 being exploited?

There is no known exploitation of CVE-2026-63349 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63349 and fix it if it is affected.

What it is: CVE-2026-63349 is a high-severity vulnerability in agronholm anyio, published on 18 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-63349 in the wild and no public exploit code.

Affected packages and fixed versions:
- anyio (PyPI): affected from 4.14.0; fixed in 4.14.2
- anyio (PyPI): affected from 4.14.0; fixed in 4.14.2
- anyio (PyPI): affected from 4.14.0; fixed in 4.14.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-63349/ (Markdown: https://insights.sbomify.com/CVE-2026-63349/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63349
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63349
- OSV: https://osv.dev/vulnerability/CVE-2026-63349

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63349/
Summaries are generated and may contain mistakes; the official description above is the record.