CVE-2026-80928 (GCVE-0-2026-80928)
Vulnerability from cvelistv5
Published
2026-09-11 19:42
Modified
2026-10-19 08:45
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: smack: fix cred UAF in smack_file_send_sigiotask() When inspecting the credentials of another task, objective credentials (->real_cred, accessed with __task_cred()) must always be used. Accessing ->cred on a non-current task is forbidden unless that task is being created or destroyed; a task is allowed to change its own ->cred pointer with no synchronization, and changing ->cred should only affect the current syscall. smack_file_send_sigiotask() was accessing both sets of credentials: First tsk->cred, then __task_cred(tsk). Fix it, always access the objective credentials here. I have tested that this bug can lead to a KASAN-reported UAF of struct cred in smack_file_send_sigiotask(), and that this fix prevents the race.
References
Impacted products
Vendor Product Version
Linux Linux Version: 3b11a1decef07c19443d24ae926982bc8ec9f4c0
Version: 3b11a1decef07c19443d24ae926982bc8ec9f4c0
Version: 3b11a1decef07c19443d24ae926982bc8ec9f4c0
Version: 3b11a1decef07c19443d24ae926982bc8ec9f4c0
Version: 3b11a1decef07c19443d24ae926982bc8ec9f4c0
Version: 3b11a1decef07c19443d24ae926982bc8ec9f4c0
Version: 3b11a1decef07c19443d24ae926982bc8ec9f4c0
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{
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmack: fix cred UAF in smack_file_send_sigiotask()\n\nWhen inspecting the credentials of another task, objective credentials\n(-\u003ereal_cred, accessed with __task_cred()) must always be used.\n\nAccessing -\u003ecred on a non-current task is forbidden unless that task is\nbeing created or destroyed; a task is allowed to change its own -\u003ecred\npointer with no synchronization, and changing -\u003ecred should only affect the\ncurrent syscall.\n\nsmack_file_send_sigiotask() was accessing both sets of credentials: First\ntsk-\u003ecred, then __task_cred(tsk).\n\nFix it, always access the objective credentials here.\n\nI have tested that this bug can lead to a KASAN-reported UAF of struct cred\nin smack_file_send_sigiotask(), and that this fix prevents the race."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Reachable only via local syscalls: fcntl(F_SETOWN)/O_ASYNC on a pipe or socket, then write or MSG_OOB so kill_fasync()/send_sigurg() call smack_file_send_sigiotask(). Same SIGIO path as CVE-2026-72183 (AV:L); a remote peer can raise SIGIO only on a socket the local attacker already owns.\nAC:L - The attacker controls both sides of the race: one thread loops faccessat() so access_override_creds() installs a non_rcu subjective cred that revert_creds()+put_cred() frees without RCU, while another thread writes the pipe or sends OOB to fire SIGIO. The fix author reproduced a KASAN cred UAF; the window is retryable.\nPR:L - pipe(), fcntl(F_SETOWN/F_SETFL), write(), and faccessat() need no capabilities. An unprivileged user namespace (unshare(CLONE_NEWUSER)) makes access() install the non_rcu override (non-root uid with caps, or real uid != fsuid). The UAF is kernel cred memory on the attacker\u2019s own task.\nUI:N - No victim action is required. The attacker arms fowner on their own file, overrides their own subjective creds via faccessat(), and triggers SIGIO themselves.\nS:U - This is in-kernel cred use-after-free leading to local privilege escalation within the kernel security authority. It is not a VM escape, IOMMU bypass, or userspace sandbox boundary crossing.\nC:H - This is a use-after-free of struct cred. After free, the cred slab can be sprayed so cred-\u003esecurity and the derived smack_known are attacker-controlled, enabling arbitrary kernel reads through smk_access() and smack_log(). Kernel UAF scores C:H.\nI:H - The same sprayed cred/task_smack/smack_known objects yield a fake-object primitive on the SIGIO path, exploitable for control-flow hijacking and arbitrary write as with other kernel cred UAFs. Kernel UAF scores I:H.\nA:H - The fix author confirmed a KASAN use-after-free of struct cred in smack_file_send_sigiotask(). Dereferencing the freed cred on the SIGIO path, including from kill_fasync() in interrupt context, causes a kernel oops or panic."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:45:12.134Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a512366d84e134a9eefc2cc40eeb6e80e2ec162c"
        },
        {
          "url": "https://git.kernel.org/stable/c/7c7fe043f3099d0d35002b248967f75e55345b93"
        },
        {
          "url": "https://git.kernel.org/stable/c/f9c7b1f2b9d8f4176d2632743f51400855978ace"
        },
        {
          "url": "https://git.kernel.org/stable/c/b5bcf3adfa27279da4401ab8f1e1a706601a92be"
        },
        {
          "url": "https://git.kernel.org/stable/c/ed64aa505875a3b4defd504ee8e59e1949246a62"
        },
        {
          "url": "https://git.kernel.org/stable/c/b791401bf389a1546a830d2b381ca60fe94c7870"
        },
        {
          "url": "https://git.kernel.org/stable/c/fedc88e38ce979a720cd2de042578cb5df3dc8de"
        }
      ],
      "title": "smack: fix cred UAF in smack_file_send_sigiotask()",
      "x_generator": {
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      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80928",
    "datePublished": "2026-09-11T19:42:04.044Z",
    "dateReserved": "2026-08-26T14:34:25.802Z",
    "dateUpdated": "2026-10-19T08:45:12.134Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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