CVE-2026-89641

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size() When the else branch of cifs_file_set_size() finds a writable file handle via find_writable_file(), it borrows tcon and server from the handle's tlink, attempts the handle-based set_file_size() RPC, and then releases the handle with cifsFileInfo_put(). If set_file_size() fails, execution falls through to the path-based fallback, which reuses the borrowed tcon and server under the "if (tcon == NULL)" guard. Since tcon is not NULL at that point, the guard is skipped. If cifsFileInfo_put() dropped the last reference on a tlink that was already removed from the tlink tree (TCON_LINK_IN_TREE cleared, as happens during reconnection or session teardown), cifs_put_tlink() will have freed tcon; the subsequent set_path_size() call is then a use-after-free. Setting tcon = NULL after cifsFileInfo_put() causes the existing guard to take the cifs_sb_tlink() path, which acquires a fresh reference for the path-based operation or fails cleanly if the session is gone.

Severity

HIGH

CVSS score

7.8 (v3.1)

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-09-11 20:19:49.867000

Last modified

2026-10-19 09:18:01.287000

View original CVE JSON

{
  "id": "CVE-2026-89641",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-11T20:19:49.867",
  "lastModified": "2026-10-19T09:18:01.287",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()\n\nWhen the else branch of cifs_file_set_size() finds a writable file handle\nvia find_writable_file(), it borrows tcon and server from the handle's\ntlink, attempts the handle-based set_file_size() RPC, and then releases\nthe handle with cifsFileInfo_put().\n\nIf set_file_size() fails, execution falls through to the path-based\nfallback, which reuses the borrowed tcon and server under the\n\"if (tcon == NULL)\" guard.  Since tcon is not NULL at that point, the\nguard is skipped.  If cifsFileInfo_put() dropped the last reference on a\ntlink that was already removed from the tlink tree (TCON_LINK_IN_TREE\ncleared, as happens during reconnection or session teardown),\ncifs_put_tlink() will have freed tcon; the subsequent set_path_size()\ncall is then a use-after-free.\n\nSetting tcon = NULL after cifsFileInfo_put() causes the existing guard\nto take the cifs_sb_tlink() path, which acquires a fresh reference for\nthe path-based operation or fails cleanly if the session is gone."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "fs/smb/client/inode.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "110fee6b9bb58a5c50047fc2594d415f741b591e",
              "lessThan": "4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "110fee6b9bb58a5c50047fc2594d415f741b591e",
              "lessThan": "4bea15d9c7683218f57b8c1f5f0aa75cab76af8d",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "110fee6b9bb58a5c50047fc2594d415f741b591e",
              "lessThan": "b96db32fed8dfb2478d7c208f89bf383beed1535",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "fs/smb/client/inode.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "6.18",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "6.18",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.50",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.4",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.3",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "attackVector": "LOCAL",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/4bea15d9c7683218f57b8c1f5f0aa75cab76af8d",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/b96db32fed8dfb2478d7c208f89bf383beed1535",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}