{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "ac89b2ef9b55924bcf922251f043ba73a32d05bb"
            },
            {
              "fixed": "a5a682b016ef5b5384e28f6d652d47a8f8e73d37"
            },
            {
              "fixed": "de79c3f3643841b8659a71958df7cf2a66bfd409"
            },
            {
              "fixed": "8d610017c992de705b304d3d727a6e3a86af6149"
            },
            {
              "fixed": "8faccac11e1369adddf5d80f4a45af93f13b2e1a"
            },
            {
              "fixed": "574aa0b4799470ac814479f1138d19efe6262255"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.17.0"
            },
            {
              "fixed": "6.6.145"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.7.0"
            },
            {
              "fixed": "6.12.97"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "fixed": "6.18.40"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.1.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72170.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\n9p: skip nlink update in cacheless mode to fix WARN_ON\n\nv9fs_dec_count() unconditionally calls drop_nlink() on regular files,\neven when the inode's nlink is already zero. In cacheless mode the\nclient refetches inode metadata from the server (the source of truth)\non every operation, so by the time v9fs_remove() returns, the locally\ncached nlink may already reflect the post-unlink value:\n\n  1. Client initiates unlink, server processes it and sets nlink to 0\n  2. Client refetches inode metadata (nlink=0) before unlink returns\n  3. Client's v9fs_remove() completes successfully\n  4. Client calls v9fs_dec_count() which calls drop_nlink() on nlink=0\n\nThis race is easily triggered under heavy unlink workloads, such as\nstress-ng's unlink stressor, producing the following warning:\n\n  WARNING: fs/inode.c:417 at drop_nlink+0x4c/0xc8\n  Call trace:\n   drop_nlink+0x4c/0xc8\n   v9fs_remove+0x1e0/0x250 [9p]\n   v9fs_vfs_unlink+0x20/0x38 [9p]\n   vfs_unlink+0x13c/0x258\n   ...\n\nIn cacheless mode the server is authoritative and the inode is on its\nway out, so locally adjusting nlink buys nothing. Skip v9fs_dec_count()\nentirely when neither CACHE_META nor CACHE_LOOSE is set, which both\navoids the warning and removes a class of nlink races (two concurrent\nunlinkers observing nlink \u003e 0 and both calling drop_nlink()) that an\nnlink == 0 guard alone would only narrow rather than close.",
  "id": "CVE-2026-72170",
  "modified": "2026-08-18T03:31:06.399052551Z",
  "published": "2026-08-15T05:53:36.332Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/574aa0b4799470ac814479f1138d19efe6262255"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8d610017c992de705b304d3d727a6e3a86af6149"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8faccac11e1369adddf5d80f4a45af93f13b2e1a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a5a682b016ef5b5384e28f6d652d47a8f8e73d37"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/de79c3f3643841b8659a71958df7cf2a66bfd409"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72170.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72170"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "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": "9p: skip nlink update in cacheless mode to fix WARN_ON"
}