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GHSA-3W57-8XMC-8V26

Vulnerability from github – Published: 2026-09-18 17:17 – Updated: 2026-09-18 17:17
VLAI
Summary
AnyIO run_process/open_process ignores extra_groups and can retain parent supplementary groups
Details

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.

Severity
7.0 (High)
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
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "anyio"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.14.0"
            },
            {
              "fixed": "4.14.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-63349"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-266",
      "CWE-269"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-18T17:17:23Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "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\u0027s 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.",
  "id": "GHSA-3w57-8xmc-8v26",
  "modified": "2026-09-18T17:17:23Z",
  "published": "2026-09-18T17:17:23Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/agronholm/anyio/security/advisories/GHSA-3w57-8xmc-8v26"
    },
    {
      "type": "WEB",
      "url": "https://github.com/agronholm/anyio/pull/1209"
    },
    {
      "type": "WEB",
      "url": "https://github.com/agronholm/anyio/commit/eb562e6462ee46b1904e50b02ce00a858cdeb200"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/agronholm/anyio"
    },
    {
      "type": "WEB",
      "url": "https://github.com/agronholm/anyio/releases/tag/4.14.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "AnyIO run_process/open_process ignores extra_groups and can retain parent supplementary groups"
}



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