Vulnerability-Lookup

GHSA-2V58-JX7R-H3CM

Vulnerability from github – Published: 2026-08-10 15:33 – Updated: 2026-08-19 18:32

Details

In the Linux kernel, the following vulnerability has been resolved:

libceph: Reject monmaps advertising zero monitors

A message of type CEPH_MSG_MON_MAP contains a monmap that is sent from a monitor to the client. This monmap contains information about the existing monitors in the cluster. Currently, a monmap indicating that there are zero monitors in the cluster is treated as valid. However, it is impossible to have zero monitors in the cluster and still receive a valid monmap from a monitor. Therefore, such a monmap must be corrupted and should be treated as invalid. Furthermore, a monmap with a monitor count of zero can subsequently crash the client when attempting to open a session with a monitor in __open_session(). This happens because the "BUG_ON(monc->monmap->num_mon < 1)" assertion in pick_new_mon() is triggered.

This patch extends a check in ceph_monmap_decode() to also reject arriving mon_maps with num_mon == 0 rather than only with num_mon > CEPH_MAX_MON.

[ idryomov: drop "log output for unusual values of num_mon" part ]

Severity

7.5 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-68155"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-10T13:20:01Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nlibceph: Reject monmaps advertising zero monitors\n\nA message of type CEPH_MSG_MON_MAP contains a monmap that is sent from a\nmonitor to the client. This monmap contains information about the\nexisting monitors in the cluster. Currently, a monmap indicating that\nthere are zero monitors in the cluster is treated as valid. However, it\nis impossible to have zero monitors in the cluster and still receive a\nvalid monmap from a monitor. Therefore, such a monmap must be corrupted\nand should be treated as invalid. Furthermore, a monmap with a monitor\ncount of zero can subsequently crash the client when attempting to open\na session with a monitor in __open_session(). This happens because the\n\"BUG_ON(monc-\u003emonmap-\u003enum_mon \u003c 1)\" assertion in pick_new_mon() is\ntriggered.\n\nThis patch extends a check in ceph_monmap_decode() to also reject\narriving mon_maps with num_mon == 0 rather than only with\nnum_mon \u003e CEPH_MAX_MON.\n\n[ idryomov: drop \"log output for unusual values of num_mon\" part ]",
  "id": "GHSA-2v58-jx7r-h3cm",
  "modified": "2026-08-19T18:32:08Z",
  "published": "2026-08-10T15:33:38Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-68155"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0591a15815b498be628a937146e44487d599ba33"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3b249546f59c3d6d3592c10657f82bc3f1faa07c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/40480eee361ed9676b3f844d532ac28b47251634"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/caf082ef8609a6ac26159ce115f55ab7d00231a3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cd0d41bc569632eaaeccde9d2a6bc919ec00c407"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e3ccd4ecab09b22f507f49cb7ed9990c7158ceab"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e67e8b694872c9bc66996040f9de9242f6236ed9"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-68155 (GCVE-0-2026-68155)

Vulnerability from cvelistv5 – Published: 2026-08-10 11:59 – Updated: 2026-08-19 16:30

Title

libceph: Reject monmaps advertising zero monitors

Summary

In the Linux kernel, the following vulnerability has been resolved: libceph: Reject monmaps advertising zero monitors A message of type CEPH_MSG_MON_MAP contains a monmap that is sent from a monitor to the client. This monmap contains information about the existing monitors in the cluster. Currently, a monmap indicating that there are zero monitors in the cluster is treated as valid. However, it is impossible to have zero monitors in the cluster and still receive a valid monmap from a monitor. Therefore, such a monmap must be corrupted and should be treated as invalid. Furthermore, a monmap with a monitor count of zero can subsequently crash the client when attempting to open a session with a monitor in __open_session(). This happens because the "BUG_ON(monc->monmap->num_mon < 1)" assertion in pick_new_mon() is triggered. This patch extends a check in ceph_monmap_decode() to also reject arriving mon_maps with num_mon == 0 rather than only with num_mon > CEPH_MAX_MON. [ idryomov: drop "log output for unusual values of num_mon" part ]

Severity

7.5 (High)


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

Assigner

Linux mitre root

References

7 references

URL	Tags
https://git.kernel.org/stable/c/caf082ef8609a6ac2…
https://git.kernel.org/stable/c/e3ccd4ecab09b22f5…
https://git.kernel.org/stable/c/0591a15815b498be6…
https://git.kernel.org/stable/c/cd0d41bc569632eaa…
https://git.kernel.org/stable/c/e67e8b694872c9bc6…
https://git.kernel.org/stable/c/3b249546f59c3d6d3…
https://git.kernel.org/stable/c/40480eee361ed9676…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: ba75bb98cfb93b62c54af25bf67ff90857264bbe , < caf082ef8609a6ac26159ce115f55ab7d00231a3 (git) Affected: ba75bb98cfb93b62c54af25bf67ff90857264bbe , < e3ccd4ecab09b22f507f49cb7ed9990c7158ceab (git) Affected: ba75bb98cfb93b62c54af25bf67ff90857264bbe , < 0591a15815b498be628a937146e44487d599ba33 (git) Affected: ba75bb98cfb93b62c54af25bf67ff90857264bbe , < cd0d41bc569632eaaeccde9d2a6bc919ec00c407 (git) Affected: ba75bb98cfb93b62c54af25bf67ff90857264bbe , < e67e8b694872c9bc66996040f9de9242f6236ed9 (git) Affected: ba75bb98cfb93b62c54af25bf67ff90857264bbe , < 3b249546f59c3d6d3592c10657f82bc3f1faa07c (git) Affected: ba75bb98cfb93b62c54af25bf67ff90857264bbe , < 40480eee361ed9676b3f844d532ac28b47251634 (git)
Linux	Linux	Affected: 2.6.34 Unaffected: 0 , < 2.6.34 (semver) Unaffected: 5.15.216 , ≤ 5.15.* (semver) Unaffected: 6.1.183 , ≤ 6.1.* (semver) Unaffected: 6.6.148 , ≤ 6.6.* (semver) Unaffected: 6.12.101 , ≤ 6.12.* (semver) Unaffected: 6.18.42 , ≤ 6.18.* (semver) Unaffected: 7.1.6 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ceph/mon_client.c"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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          "versions": [
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              "status": "affected",
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              "versionType": "git"
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              "status": "affected",
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              "versionType": "git"
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              "status": "affected",
              "version": "2.6.34"
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "5.15.216",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "6.1.183",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.148",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "6.12.101",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.1.6",
              "versionType": "semver"
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            {
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        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
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              "value": "AV:N - The bug is reached when libceph decodes CEPH_MSG_MON_MAP from a remote Ceph monitor over the kernel client\u0027s established TCP/msgr2 session (mon_dispatch -\u003e ceph_monc_handle_map -\u003e ceph_monmap_decode), which is a network protocol attack surface on CephFS/RBD/cloud nodes.\nAC:L - An attacker who can send monitor protocol messages only needs to set num_mon=0 in the monmap; once accepted, any later session reopen (keepalive timeout, hunt, or connection fault) deterministically hits BUG_ON in pick_new_mon without races or special memory layout.\nPR:N - In the highest-impact scenario a malicious or compromised Ceph monitor (or equivalent authenticated cluster peer) sends the malformed monmap to already-connected kernel clients; the attacker needs no local privileges on the victim host.\nUI:N - After a Ceph client session exists, monmap updates are delivered and processed automatically by the kernel monitor client; no further mount, open, or other victim interaction is required to accept the bad map and later crash on reconnect.\nS:U - Exploitation causes a kernel BUG/panic within the same kernel security domain and does not cross VM, container, IOMMU, or other security boundaries.\nC:N - The failure mode is a BUG_ON assertion in pick_new_mon when num_mon is zero; there is no memory corruption, out-of-bounds access, or other information disclosure primitive on the vulnerable path.\nI:N - Accepting num_mon==0 only stores an empty monmap and later triggers a deliberate kernel BUG; attacker input does not corrupt or modify arbitrary kernel memory or enable code execution.\nA:H - BUG_ON(monc-\u003emonmap-\u003enum_mon \u003c 1) in pick_new_mon during __open_session causes a kernel oops/panic, fully denying availability of the affected host until reboot."
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        "dateUpdated": "2026-08-19T16:30:22.933Z",
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          "url": "https://git.kernel.org/stable/c/40480eee361ed9676b3f844d532ac28b47251634"
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      "title": "libceph: Reject monmaps advertising zero monitors",
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    "datePublished": "2026-08-10T11:59:21.200Z",
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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.

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GHSA-2V58-JX7R-H3CM

CVE-2026-68155 (GCVE-0-2026-68155)

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Nomenclature