{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "1d17de9534cb5a4c4c380d174cc2f9281b34f89e"
            },
            {
              "fixed": "dc5c7dffda92ef372fa587c444a1c537373df824"
            },
            {
              "fixed": "c37db86d2b5e9b57001ccae7e7a727e95a4f9c02"
            },
            {
              "fixed": "5f892c767b30e4fb0c744c59f9235c717383d2cd"
            },
            {
              "fixed": "77933e22adfe813be2bd10be08d6e950103c3967"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.10.0"
            },
            {
              "fixed": "6.12.109"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "fixed": "6.18.50"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.2.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89651.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: bound MDSCapAuth path and fs_name decode in handle_session()\n\nhandle_session() decodes the MDSCapAuth records carried by a\nCEPH_SESSION_OPEN message (msg_version \u003e= 6). For each record the\nmatch.path and match.fs_name byte strings are read by first decoding a\n32-bit length and then copying that many bytes with the bare\nceph_decode_copy(). Unlike the surrounding fields, which all use the\n_safe decode variants, these two copies are not preceded by a\nceph_decode_need() bounds check, and the enclosing MDSCapAuth and\nMDSCapMatch struct_len fields are skipped rather than enforced as an\nupper bound. A length larger than the bytes remaining in the message\nfront makes ceph_decode_copy() read past the end of the front buffer.\n\nThe message front is a dedicated allocation (ceph_msg_new2() -\u003e\nkvmalloc), so the over-read runs off that object. A malicious or\ncompromised MDS can trigger this with the first post-connect message on\nmount, with no client-side user interaction; under KASAN it is reported\nas a slab-out-of-bounds read in handle_session().\n\nImpact: a malicious MDS can force the kernel client to read up to 4 GiB\npast the message front allocation during session setup, crashing the\nclient (out-of-bounds read).\n\nSwitch both copies to ceph_decode_copy_safe(), which performs the\nceph_decode_need() bounds check before the copy and branches to the\nexisting bad label, matching the rest of the decoder and the error path\nthat frees the partially decoded cap_auths array.",
  "id": "CVE-2026-89651",
  "modified": "2026-09-15T03:31:01.326068410Z",
  "published": "2026-09-11T19:45:41.620Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5f892c767b30e4fb0c744c59f9235c717383d2cd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/77933e22adfe813be2bd10be08d6e950103c3967"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c37db86d2b5e9b57001ccae7e7a727e95a4f9c02"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dc5c7dffda92ef372fa587c444a1c537373df824"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89651.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89651"
    },
    {
      "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:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "ceph: bound MDSCapAuth path and fs_name decode in handle_session()"
}