PYSEC-2026-3540

Vulnerability from pysec - Published: 2026-07-23 11:41 - Updated: 2026-07-23 14:33
VLAI
Details

Impact

The _uid option performed an incomplete privilege drop on Linux/Unix-like systems.

When sh was run from a process with elevated privileges, such as root, and a command was launched with _uid=<unprivileged user>, the child process changed its UID and primary GID but did not reset its supplementary groups. As a result, the child process could retain the parent process’s supplementary groups, potentially including privileged groups such as root, docker, disk, shadow, or sudo.

This could allow a subprocess that was expected to run with reduced privileges to access files or resources available to the original process’s supplementary groups. Users are impacted if they rely on _uid as a privilege boundary when launching commands from a privileged parent process.

Patches

Upgrade to version >= 2.2.4

Workarounds

Avoid using _uid when the user represents a less-privileged user.

Severity
7.9 (High)
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N
Impacted products
Name purl
sh pkg:pypi/sh
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "sh",
        "purl": "pkg:pypi/sh"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.2.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.01",
        "0.106",
        "0.107",
        "0.108",
        "1.0",
        "1.01",
        "1.02",
        "1.03",
        "1.04",
        "1.05",
        "1.06",
        "1.07",
        "1.08",
        "1.09",
        "1.10",
        "1.11",
        "1.12.0",
        "1.12.1",
        "1.12.10",
        "1.12.11",
        "1.12.12",
        "1.12.13",
        "1.12.14",
        "1.12.2",
        "1.12.3",
        "1.12.4",
        "1.12.5",
        "1.12.6",
        "1.12.7",
        "1.12.8",
        "1.12.9",
        "1.13.0",
        "1.13.1",
        "1.14.0",
        "1.14.1",
        "1.14.2",
        "1.14.3",
        "2.0.0",
        "2.0.1",
        "2.0.2",
        "2.0.3",
        "2.0.4",
        "2.0.5",
        "2.0.6",
        "2.0.7",
        "2.1.0",
        "2.2.0",
        "2.2.1",
        "2.2.2",
        "2.2.3"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54552",
    "GHSA-q38v-wp89-2w55"
  ],
  "details": "### Impact\nThe `_uid` option performed an incomplete privilege drop on Linux/Unix-like systems.\n\nWhen `sh` was run from a process with elevated privileges, such as root, and a command was launched with `_uid=\u003cunprivileged user\u003e`, the child process changed its UID and primary GID but did not reset its supplementary groups. As a result, the child process could retain the parent process\u2019s supplementary groups, potentially including privileged groups such as root, docker, disk, shadow, or sudo.\n\nThis could allow a subprocess that was expected to run with reduced privileges to access files or resources available to the original process\u2019s supplementary groups. Users are impacted if they rely on `_uid` as a privilege boundary when launching commands from a privileged parent process.\n\n### Patches\nUpgrade to version \u003e= 2.2.4\n\n### Workarounds\nAvoid using `_uid` when the user represents a less-privileged user.",
  "id": "PYSEC-2026-3540",
  "modified": "2026-07-23T14:33:04.660547Z",
  "published": "2026-07-23T11:41:46.915478Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/amoffat/sh/security/advisories/GHSA-q38v-wp89-2w55"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/amoffat/sh"
    },
    {
      "type": "WEB",
      "url": "https://github.com/amoffat/sh/releases/tag/2.2.4"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/sh"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-q38v-wp89-2w55"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54552"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "sh _uid does not drop supplementary groups (incomplete privilege drop)"
}



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