CVE-2026-89654

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: ceph: fix UAF in check_new_map() on session freed during unlock check_new_map() iterates mdsc->sessions[] and for each active session drops mdsc->mutex to perform per-session operations. The forced-close path (rank removed from map) correctly takes a reference on s via ceph_get_mds_session() before releasing mdsc->mutex, but three other paths do not: Path A (address changed): mutex_unlock → mutex_lock(&s->s_mutex) Path B (reconnect): mutex_unlock → send_mds_reconnect(mdsc, s) Path C (active transition): mutex_unlock → mutex_lock(&s->s_mutex) Without the extra reference, another thread can acquire mdsc->mutex during the unlock window, call __unregister_session() which drops the last reference on s, and free it. The original thread then accesses freed memory via s->s_mutex. Fix by adding ceph_get_mds_session(s) before each mutex_unlock and ceph_put_mds_session(s) after the corresponding mutex_lock, matching the pattern already used in the forced-close path. Race timeline (Path A): Thread A (check_new_map) Thread B (another map update holds mdsc->mutex or session teardown) -------------------------- -------------------------- s = mdsc->sessions[i] (refcount == 1, held only by sessions[] array) mutex_unlock(&mdsc->mutex) ---> acquires mdsc->mutex __unregister_session(mdsc, s) sessions[i] = NULL ceph_put_mds_session(s) refcount: 1 -> 0 kfree(s) <--- freed! mutex_lock(&s->s_mutex) UAF on freed s->s_mutex

Severity

CRITICAL

CVSS score

9.8 (v3.1)

Vulnerability status

Received

Source identifier

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

Published

2026-09-11 20:19:51.540000

Last modified

2026-10-30 13:20:24.920000

View original CVE JSON

{
  "id": "CVE-2026-89654",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-11T20:19:51.540",
  "lastModified": "2026-10-30T13:20:24.920",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: fix UAF in check_new_map() on session freed during unlock\n\ncheck_new_map() iterates mdsc->sessions[] and for each active session\ndrops mdsc->mutex to perform per-session operations.  The forced-close\npath (rank removed from map) correctly takes a reference on s via\nceph_get_mds_session() before releasing mdsc->mutex, but three other\npaths do not:\n\n  Path A (address changed):  mutex_unlock → mutex_lock(&s->s_mutex)\n  Path B (reconnect):        mutex_unlock → send_mds_reconnect(mdsc, s)\n  Path C (active transition): mutex_unlock → mutex_lock(&s->s_mutex)\n\nWithout the extra reference, another thread can acquire mdsc->mutex\nduring the unlock window, call __unregister_session() which drops the\nlast reference on s, and free it.  The original thread then accesses\nfreed memory via s->s_mutex.\n\nFix by adding ceph_get_mds_session(s) before each mutex_unlock and\nceph_put_mds_session(s) after the corresponding mutex_lock, matching\nthe pattern already used in the forced-close path.\n\nRace timeline (Path A):\n\n  Thread A (check_new_map)             Thread B (another map update\n    holds mdsc->mutex                      or session teardown)\n  --------------------------           --------------------------\n  s = mdsc->sessions[i]\n  (refcount == 1, held only by\n   sessions[] array)\n\n  mutex_unlock(&mdsc->mutex)\n                               --->    acquires mdsc->mutex\n                                       __unregister_session(mdsc, s)\n                                         sessions[i] = NULL\n                                         ceph_put_mds_session(s)\n                                           refcount: 1 -> 0\n                                           kfree(s)  <--- freed!\n\n  mutex_lock(&s->s_mutex)\n  UAF on freed s->s_mutex"
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "fs/ceph/mds_client.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "2f2dc053404febedc9c273452d9d518fb31fde72",
              "lessThan": "989343b7ee5b1a08778be0c7c4bf6030d3910807",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2f2dc053404febedc9c273452d9d518fb31fde72",
              "lessThan": "352a278d5a1965aae3f817ce5d24a67ee42d45d1",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2f2dc053404febedc9c273452d9d518fb31fde72",
              "lessThan": "820871e9dbeecd2533c4c5f5d91878ceaf02324c",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2f2dc053404febedc9c273452d9d518fb31fde72",
              "lessThan": "9646dfee880730aae4b379a4b8ee6c88ac735acd",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2f2dc053404febedc9c273452d9d518fb31fde72",
              "lessThan": "21d5be092d947f8d83f76f7ebf3989e7e9230a98",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2f2dc053404febedc9c273452d9d518fb31fde72",
              "lessThan": "ee611a7509554c4ca1f54f6aefe592fb1df7ea70",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "fs/ceph/mds_client.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "2.6.34",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "2.6.34",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.191",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.160",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.114",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.57",
              "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:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-10-16T19:25:25.205939Z",
          "id": "CVE-2026-89654",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/21d5be092d947f8d83f76f7ebf3989e7e9230a98",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/352a278d5a1965aae3f817ce5d24a67ee42d45d1",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/820871e9dbeecd2533c4c5f5d91878ceaf02324c",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/9646dfee880730aae4b379a4b8ee6c88ac735acd",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/989343b7ee5b1a08778be0c7c4bf6030d3910807",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/ee611a7509554c4ca1f54f6aefe592fb1df7ea70",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}