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  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63827.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: fix use-after-free in rawdata dedup loop\n\naa_replace_profiles() walks ns-\u003erawdata_list to dedup the incoming\npolicy blob against entries already attached to existing profiles.\nPer the kernel-doc on struct aa_loaddata, list membership does not\nhold a reference: profiles hold pcount, and when the last pcount\ndrops, do_ploaddata_rmfs() is queued on a workqueue that takes\nns-\u003elock and removes the entry. Between dropping the last pcount\nand the workqueue running, an entry remains on the list with\npcount == 0.\n\naa_get_profile_loaddata() is an unconditional kref_get() on\npcount, so when the dedup loop hits such an entry, refcount\nhardening reports\n\n  refcount_t: addition on 0; use-after-free.\n\ninside aa_replace_profiles(), and the poisoned counter then\ntrips \"saturated\" and \"underflow\" warnings on the subsequent\nuses of the same loaddata.\n\nBefore commit a0b7091c4de4 (\"apparmor: fix race on rawdata\ndereference\") the dedup path used a get_unless_zero-style helper\non a single counter, so the existing \"if (tmp)\" guard was\nmeaningful. The split-refcount refactor introduced\naa_get_profile_loaddata(), which has plain kref_get() semantics,\nand the guard quietly became a no-op.\n\nIntroduce aa_get_profile_loaddata_not0(), matching the existing\n_not0 convention used by aa_get_profile_not0(), and use it for\nthe rawdata_list dedup lookup so dying entries are skipped.\n\nReproduced on x86_64 with v7.1-rc5 in QEMU+KVM running Ubuntu\n24.04 + stress-ng 0.17.06:\n\n  stress-ng --apparmor 1 --klog-check --timeout 60s\n\nWithout this patch the three refcount_t warnings fire within a\nfew seconds. With it the same 60 s run is clean. Coverage is a\nsmoke-test only; a longer soak with CONFIG_KASAN, CONFIG_KCSAN\nand CONFIG_PROVE_LOCKING would be welcome from anyone with the\ncycles.",
  "id": "CVE-2026-63827",
  "modified": "2026-07-22T05:30:03.436434765Z",
  "published": "2026-07-19T12:02:22.083Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/15fd83a1e42ede15070968806bb6c8b1a5170688"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5e34fa9f6f7cd688ae153fff13139a5cf2d42339"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6f060496d03e4dc560a40f73770bd08335cb7a27"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a7a2890028f16e5b0af0bb005d80fcb32559cca3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c3ca2631073b2cef06824fd2bfc452ff7a1023de"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ce261a20b41db522e320a41bbf1292bf85af66df"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63827.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63827"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.8.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "apparmor: fix use-after-free in rawdata dedup loop"
}