CVE-2026-89766 (GCVE-0-2026-89766)
Vulnerability from cvelistv5
Published
2026-09-11 19:47
Modified
2026-10-19 08:52
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: pidfd: hold exec_update_lock around namespace ioctl The PIDFD_GET_*_NAMESPACE ioctls in pidfd_ioctl() perform a filesystem credentials ptrace access check before handing out a namespace file descriptor. The accompanying comment states that the code "mirrors nsfs behavior", but, unlike the corresponding procfs paths, it does so without holding the target task's exec_update_lock. proc_ns_get_link() and proc_ns_readlink() both take exec_update_lock for reading around the ptrace check and the namespace lookup, so that the credentials used for the access decision match those of the task when its namespace is read. Without it, a caller can pass the check against the target's old credentials and then read the namespace after the target has execve()'d a setuid binary and committed new credentials -- accessing namespace information it should have been denied. Hold exec_update_lock for reading around the ptrace check and the namespace lookup so that pidfd truly mirrors nsfs behavior, as the comment already claims. open_namespace() itself runs outside the lock: once a namespace reference is obtained it carries its own refcount and is opened with the caller's own credentials, so a concurrent execve() on the target can no longer affect the outcome.
References
Impacted products
Vendor Product Version
Linux Linux Version: 5b08bd408534bfb3a7cf5778da5b27d4e4fffe12
Version: 5b08bd408534bfb3a7cf5778da5b27d4e4fffe12
Version: 5b08bd408534bfb3a7cf5778da5b27d4e4fffe12
Version: 5b08bd408534bfb3a7cf5778da5b27d4e4fffe12
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/pidfs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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        {
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          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "6.11"
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.12.112",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
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            {
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              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
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      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.112",
                  "versionStartIncluding": "6.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.51",
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
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                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npidfd: hold exec_update_lock around namespace ioctl\n\nThe PIDFD_GET_*_NAMESPACE ioctls in pidfd_ioctl() perform a filesystem\ncredentials ptrace access check before handing out a namespace file\ndescriptor.  The accompanying comment states that the code \"mirrors nsfs\nbehavior\", but, unlike the corresponding procfs paths, it does so without\nholding the target task\u0027s exec_update_lock.\n\nproc_ns_get_link() and proc_ns_readlink() both take exec_update_lock for\nreading around the ptrace check and the namespace lookup, so that the\ncredentials used for the access decision match those of the task when its\nnamespace is read.  Without it, a caller can pass the check against the\ntarget\u0027s old credentials and then read the namespace after the target has\nexecve()\u0027d a setuid binary and committed new credentials -- accessing\nnamespace information it should have been denied.\n\nHold exec_update_lock for reading around the ptrace check and the\nnamespace lookup so that pidfd truly mirrors nsfs behavior, as the comment\nalready claims.  open_namespace() itself runs outside the lock: once a\nnamespace reference is obtained it carries its own refcount and is opened\nwith the caller\u0027s own credentials, so a concurrent execve() on the target\ncan no longer affect the outcome."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:52:19.816Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/bac2f1913a216677c2c220d7bb352dd0330065ca"
        },
        {
          "url": "https://git.kernel.org/stable/c/cf24ce48d60225fdbee68ed2058763a1fd172ff3"
        },
        {
          "url": "https://git.kernel.org/stable/c/e89318aa8629969e86548b05e7c19283af3f0efb"
        },
        {
          "url": "https://git.kernel.org/stable/c/9688a46802939da28f00cb40e8129615d5d4af39"
        }
      ],
      "title": "pidfd: hold exec_update_lock around namespace ioctl",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89766",
    "datePublished": "2026-09-11T19:47:06.597Z",
    "dateReserved": "2026-09-11T19:38:34.764Z",
    "dateUpdated": "2026-10-19T08:52:19.816Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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