Vulnerability-Lookup

FKIE_CVE-2026-89651

Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-09-13 07:17

Severity

9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: ceph: bound MDSCapAuth path and fs_name decode in handle_session() handle_session() decodes the MDSCapAuth records carried by a CEPH_SESSION_OPEN message (msg_version >= 6). For each record the match.path and match.fs_name byte strings are read by first decoding a 32-bit length and then copying that many bytes with the bare ceph_decode_copy(). Unlike the surrounding fields, which all use the _safe decode variants, these two copies are not preceded by a ceph_decode_need() bounds check, and the enclosing MDSCapAuth and MDSCapMatch struct_len fields are skipped rather than enforced as an upper bound. A length larger than the bytes remaining in the message front makes ceph_decode_copy() read past the end of the front buffer. The message front is a dedicated allocation (ceph_msg_new2() -> kvmalloc), so the over-read runs off that object. A malicious or compromised MDS can trigger this with the first post-connect message on mount, with no client-side user interaction; under KASAN it is reported as a slab-out-of-bounds read in handle_session(). Impact: a malicious MDS can force the kernel client to read up to 4 GiB past the message front allocation during session setup, crashing the client (out-of-bounds read). Switch both copies to ceph_decode_copy_safe(), which performs the ceph_decode_need() bounds check before the copy and branches to the existing bad label, matching the rest of the decoder and the error path that frees the partially decoded cap_auths array.

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/5f892c767b30e4fb0c744c59f9235c717383d2cd
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/77933e22adfe813be2bd10be08d6e950103c3967
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/c37db86d2b5e9b57001ccae7e7a727e95a4f9c02
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/dc5c7dffda92ef372fa587c444a1c537373df824

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ceph/mds_client.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "dc5c7dffda92ef372fa587c444a1c537373df824",
              "status": "affected",
              "version": "1d17de9534cb5a4c4c380d174cc2f9281b34f89e",
              "versionType": "git"
            },
            {
              "lessThan": "c37db86d2b5e9b57001ccae7e7a727e95a4f9c02",
              "status": "affected",
              "version": "1d17de9534cb5a4c4c380d174cc2f9281b34f89e",
              "versionType": "git"
            },
            {
              "lessThan": "5f892c767b30e4fb0c744c59f9235c717383d2cd",
              "status": "affected",
              "version": "1d17de9534cb5a4c4c380d174cc2f9281b34f89e",
              "versionType": "git"
            },
            {
              "lessThan": "77933e22adfe813be2bd10be08d6e950103c3967",
              "status": "affected",
              "version": "1d17de9534cb5a4c4c380d174cc2f9281b34f89e",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/ceph/mds_client.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.10"
            },
            {
              "lessThan": "6.10",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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",
  "lastModified": "2026-09-13T07:17:30.417",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-11T20:19:51.150",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/5f892c767b30e4fb0c744c59f9235c717383d2cd"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/77933e22adfe813be2bd10be08d6e950103c3967"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c37db86d2b5e9b57001ccae7e7a727e95a4f9c02"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/dc5c7dffda92ef372fa587c444a1c537373df824"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

CVE-2026-89651 (GCVE-0-2026-89651)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:45 – Updated: 2026-09-13 06:32

Title

ceph: bound MDSCapAuth path and fs_name decode in handle_session()

Summary

Severity

9.8 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

4 references

URL	Tags
https://git.kernel.org/stable/c/dc5c7dffda92ef372…
https://git.kernel.org/stable/c/c37db86d2b5e9b570…
https://git.kernel.org/stable/c/5f892c767b30e4fb0…
https://git.kernel.org/stable/c/77933e22adfe813be…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 1d17de9534cb5a4c4c380d174cc2f9281b34f89e , < dc5c7dffda92ef372fa587c444a1c537373df824 (git) Affected: 1d17de9534cb5a4c4c380d174cc2f9281b34f89e , < c37db86d2b5e9b57001ccae7e7a727e95a4f9c02 (git) Affected: 1d17de9534cb5a4c4c380d174cc2f9281b34f89e , < 5f892c767b30e4fb0c744c59f9235c717383d2cd (git) Affected: 1d17de9534cb5a4c4c380d174cc2f9281b34f89e , < 77933e22adfe813be2bd10be08d6e950103c3967 (git)
Linux	Linux	Affected: 6.10 Unaffected: 0 , < 6.10 (semver) Unaffected: 6.12.109 , ≤ 6.12.* (semver) Unaffected: 6.18.50 , ≤ 6.18.* (semver) Unaffected: 7.2.4 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ceph/mds_client.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "dc5c7dffda92ef372fa587c444a1c537373df824",
              "status": "affected",
              "version": "1d17de9534cb5a4c4c380d174cc2f9281b34f89e",
              "versionType": "git"
            },
            {
              "lessThan": "c37db86d2b5e9b57001ccae7e7a727e95a4f9c02",
              "status": "affected",
              "version": "1d17de9534cb5a4c4c380d174cc2f9281b34f89e",
              "versionType": "git"
            },
            {
              "lessThan": "5f892c767b30e4fb0c744c59f9235c717383d2cd",
              "status": "affected",
              "version": "1d17de9534cb5a4c4c380d174cc2f9281b34f89e",
              "versionType": "git"
            },
            {
              "lessThan": "77933e22adfe813be2bd10be08d6e950103c3967",
              "status": "affected",
              "version": "1d17de9534cb5a4c4c380d174cc2f9281b34f89e",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/ceph/mds_client.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.10"
            },
            {
              "lessThan": "6.10",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.109",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - CEPH_MSG_CLIENT_SESSION arrives over the kernel Ceph messenger TCP session from an MDS peer; mds_dispatch() hands it to handle_session(), so a malicious or compromised MDS (or on-path attacker on an unsigned msgr session) reaches the unbounded decode with network data alone.\nAC:L - The attacker fully controls msg-\u003ehdr.version and the MDSCapAuth path/fs_name u32 lengths; setting version\u003e=6 and a length larger than remaining front bytes (or UINT_MAX) deterministically hits the unchecked ceph_decode_copy() with no race or layout dependency.\nPR:N - Exploitation requires only sending a crafted CEPH_SESSION_OPEN as the remote MDS peer on an established session; the attacker needs no account, capability, or mount privilege on the victim beyond the client already being connected to that cluster.\nUI:N - Once CephFS is mounted (standard in Rook/Kubernetes/OpenStack), the MDS emits CEPH_SESSION_OPEN as the first post-connect message on mount or reconnect, processed automatically in the ceph-msgr kworker with no further victim action at exploit time.\nS:U - The out-of-bounds read and any resulting kernel memory corruption stay inside the victim host\u0027s CephFS client kernel; they do not cross a VM, sandbox, or IOMMU security boundary.\nC:H - Unchecked ceph_decode_copy() of an attacker-chosen u32 length reads past the kvmalloc\u0027d message front into adjacent kernel memory and stores those bytes in match.path/match.fs_name; unbounded out-of-bounds reads are High per kernel guidance.\nI:H - Attacker-controlled _len is both the memcpy size and kcalloc(_len+1) count, so UINT_MAX wraps the allocation to ZERO_SIZE_PTR and the copy writes from address 16; over-read bytes are also installed as cap-auth path/fs_name used by ceph_mds_check_access, a memory-corruption primitive.\nA:H - The over-read runs off the dedicated message-front object and can fault on unmapped pages or vmalloc guard pages, oopsing the ceph-msgr worker as KASAN reported; a malicious MDS can repeat this on every session open."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:32:30.623Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/dc5c7dffda92ef372fa587c444a1c537373df824"
        },
        {
          "url": "https://git.kernel.org/stable/c/c37db86d2b5e9b57001ccae7e7a727e95a4f9c02"
        },
        {
          "url": "https://git.kernel.org/stable/c/5f892c767b30e4fb0c744c59f9235c717383d2cd"
        },
        {
          "url": "https://git.kernel.org/stable/c/77933e22adfe813be2bd10be08d6e950103c3967"
        }
      ],
      "title": "ceph: bound MDSCapAuth path and fs_name decode in handle_session()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89651",
    "datePublished": "2026-09-11T19:45:41.620Z",
    "dateReserved": "2026-09-11T19:38:34.742Z",
    "dateUpdated": "2026-09-13T06:32:30.623Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.