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GHSA-W8VV-X828-GJPF

Vulnerability from github – Published: 2025-10-21 12:31 – Updated: 2025-10-21 12:31
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

exec: Force single empty string when argv is empty

Quoting[1] Ariadne Conill:

"In several other operating systems, it is a hard requirement that the second argument to execve(2) be the name of a program, thus prohibiting a scenario where argc < 1. POSIX 2017 also recommends this behaviour, but it is not an explicit requirement[2]:

The argument arg0 should point to a filename string that is
associated with the process being started by one of the exec
functions.

... Interestingly, Michael Kerrisk opened an issue about this in 2008[3], but there was no consensus to support fixing this issue then. Hopefully now that CVE-2021-4034 shows practical exploitative use[4] of this bug in a shellcode, we can reconsider.

This issue is being tracked in the KSPP issue tracker[5]."

While the initial code searches[6][7] turned up what appeared to be mostly corner case tests, trying to that just reject argv == NULL (or an immediately terminated pointer list) quickly started tripping[8] existing userspace programs.

The next best approach is forcing a single empty string into argv and adjusting argc to match. The number of programs depending on argc == 0 seems a smaller set than those calling execve with a NULL argv.

Account for the additional stack space in bprm_stack_limits(). Inject an empty string when argc == 0 (and set argc = 1). Warn about the case so userspace has some notice about the change:

process './argc0' launched './argc0' with NULL argv: empty string added

Additionally WARN() and reject NULL argv usage for kernel threads.

[1] https://lore.kernel.org/lkml/20220127000724.15106-1-ariadne@dereferenced.org/ [2] https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html [3] https://bugzilla.kernel.org/show_bug.cgi?id=8408 [4] https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt [5] https://github.com/KSPP/linux/issues/176 [6] https://codesearch.debian.net/search?q=execve%5C+%5C%28%5B%5E%2C%5D%2B%2C+NULL&literal=0 [7] https://codesearch.debian.net/search?q=execlp%3F%5Cs%5C%28%5B%5E%2C%5D%2B%2C%5CsNULL&literal=0 [8] https://lore.kernel.org/lkml/20220131144352.GE16385@xsang-OptiPlex-9020/

Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Show details on source website
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{
  "affected": [],
  "aliases": [
    "CVE-2022-49264"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-476"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-02-26T07:01:03Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nexec: Force single empty string when argv is empty\n\nQuoting[1] Ariadne Conill:\n\n\"In several other operating systems, it is a hard requirement that the\nsecond argument to execve(2) be the name of a program, thus prohibiting\na scenario where argc \u003c 1. POSIX 2017 also recommends this behaviour,\nbut it is not an explicit requirement[2]:\n\n    The argument arg0 should point to a filename string that is\n    associated with the process being started by one of the exec\n    functions.\n...\nInterestingly, Michael Kerrisk opened an issue about this in 2008[3],\nbut there was no consensus to support fixing this issue then.\nHopefully now that CVE-2021-4034 shows practical exploitative use[4]\nof this bug in a shellcode, we can reconsider.\n\nThis issue is being tracked in the KSPP issue tracker[5].\"\n\nWhile the initial code searches[6][7] turned up what appeared to be\nmostly corner case tests, trying to that just reject argv == NULL\n(or an immediately terminated pointer list) quickly started tripping[8]\nexisting userspace programs.\n\nThe next best approach is forcing a single empty string into argv and\nadjusting argc to match. The number of programs depending on argc == 0\nseems a smaller set than those calling execve with a NULL argv.\n\nAccount for the additional stack space in bprm_stack_limits(). Inject an\nempty string when argc == 0 (and set argc = 1). Warn about the case so\nuserspace has some notice about the change:\n\n    process \u0027./argc0\u0027 launched \u0027./argc0\u0027 with NULL argv: empty string added\n\nAdditionally WARN() and reject NULL argv usage for kernel threads.\n\n[1] https://lore.kernel.org/lkml/20220127000724.15106-1-ariadne@dereferenced.org/\n[2] https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html\n[3] https://bugzilla.kernel.org/show_bug.cgi?id=8408\n[4] https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt\n[5] https://github.com/KSPP/linux/issues/176\n[6] https://codesearch.debian.net/search?q=execve%5C+*%5C%28%5B%5E%2C%5D%2B%2C+*NULL\u0026literal=0\n[7] https://codesearch.debian.net/search?q=execlp%3F%5Cs*%5C%28%5B%5E%2C%5D%2B%2C%5Cs*NULL\u0026literal=0\n[8] https://lore.kernel.org/lkml/20220131144352.GE16385@xsang-OptiPlex-9020/",
  "id": "GHSA-w8vv-x828-gjpf",
  "modified": "2025-10-21T12:31:24Z",
  "published": "2025-10-21T12:31:24Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-49264"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1290eb4412aa0f0e9f3434b406dc8e255da85f9e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1fe82bfd9e4ce93399d815ca458b58505191c3e8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/27a6f495b63a1804cc71be45911065db7757a98c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/41f6ea5b9aaa28b740d47ffe995a5013211fdbb0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/98e0c7c702894987732776736c99b85ade6fba45"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a8054d3fa5deb84b215d6be1b910a978f3cb840d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b50fb8dbc8b81aaa126387de428f4c42a7c72a73"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cfbfff8ce5e3d674947581f1eb9af0a1b1807950"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dcd46d897adb70d63e025f175a00a89797d31a43"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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