apparmor: fix side-effect bug in match_char() macro usage

{
  "id": "d4f95ca53fc68ed0ca2330438fc74609144b7a829b6d6357f79fa06c91d2258a",
  "url": "https://osv.dev/vulnerability/CVE-2026-23406",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "apparmor: fix side-effect bug in match_char() macro usage",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: apparmor: fix side-effect bug in match_char() macro usage The match_char() macro evaluates its character parameter multiple times when traversing differential encoding chains. When invoked with *str++, the string pointer advances on each iteration of the inner do-while loop, causing the DFA to check different characters at each iteration and therefore skip input characters. This results in out-of-bounds reads when the pointer advances past the input buffer boundary. [ 94.984676] ================================================================== [ 94.985301] BUG: KASAN: slab-out-of-bounds in aa_dfa_match+0x5ae/0x760 [ 94.985655] Read of size 1 at addr ffff888100342000 by task file/976 [ 94.986319] CPU: 7 UID: 1000 PID: 976 Comm: file Not tainted 6.19.0-rc7-next-20260127 #1 PREEMPT(lazy) [ 94.986322] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 94.986329] Call Trace: [ 94.986341] [ 94.986347] dump_stack_lvl+0x5e/0x80 [ 94.986374] print_report+0xc8/0x270 [ 94.986384] ? aa_dfa_match+0x5ae/0x760 [ 94.986388] kasan_report+0x118/0x150 [ 94.986401] ? aa_dfa_match+0x5ae/0x760 [ 94.986405] aa_dfa_match+0x5ae/0x760 [ 94.986408] __aa_path_perm+0x131/0x400 [ 94.986418] aa_path_perm+0x219/0x2f0 [ 94.986424] apparmor_file_open+0x345/0x570 [ 94.986431] security_file_open+0x5c/0x140 [ 94.986442] do_dentry_open+0x2f6/0x1120 [ 94.986450] vfs_open+0x38/0x2b0 [ 94.986453] ? may_open",
    "evidence": "osv:CVE-2026-23406",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.253",
            "evidence": "/affected/1/ranges"
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          {
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            "evidence": "/affected/1/ranges"
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            "evidence": "/affected/1/ranges"
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            "evidence": "/affected/1/ranges"
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            "evidence": "/affected/1/ranges"
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          {
            "value": "6.18.18",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.8",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-23406",
      "aliases": [
        "CVE-2026-23406"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                {
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                },
                {
                  "fixed": "f16f2e5936c0f5f0d11fdf10d2be3e47e7108e42"
                },
                {
                  "fixed": "1fc94f16098213d01e56c97feed9b3ecf0147a37"
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                {
                  "fixed": "5a184f7cbdeaad17e16dedf3c17d0cd622edfed8"
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                {
                  "fixed": "b73c1dff8a9d7eeaebabf8097a5b2de192f40913"
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                {
                  "fixed": "0510d1ba0976f97f521feb2b75b0572ea5df3ceb"
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                {
                  "fixed": "383b7270faf42564f133134c2fc3c24bbae52615"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23406.json"
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        },
        {
          "ranges": [
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              "type": "ECOSYSTEM",
              "events": [
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          "package": {
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            "ecosystem": "Linux"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23406.json"
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      ],
      "modified": "2026-10-28T02:30:29.539652349Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0510d1ba0976f97f521feb2b75b0572ea5df3ceb",
        "https://git.kernel.org/stable/c/1fc94f16098213d01e56c97feed9b3ecf0147a37",
        "https://git.kernel.org/stable/c/383b7270faf42564f133134c2fc3c24bbae52615",
        "https://git.kernel.org/stable/c/5a184f7cbdeaad17e16dedf3c17d0cd622edfed8",
        "https://git.kernel.org/stable/c/8756b68edae37ff546c02091989a4ceab3f20abd",
        "https://git.kernel.org/stable/c/b73c1dff8a9d7eeaebabf8097a5b2de192f40913",
        "https://git.kernel.org/stable/c/c7dc56d8b37eda1396feeec3ab1c7ecee5eae31b",
        "https://git.kernel.org/stable/c/f16f2e5936c0f5f0d11fdf10d2be3e47e7108e42",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23406.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-23406",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23406.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-23406",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 496015,
  "published_at": "2026-04-01T08:36:36.46+00:00"
}