CVE-2026-68155 (GCVE-0-2026-68155)
Vulnerability from cvelistv5 – Published: 2026-08-10 11:59 – Updated: 2026-08-19 16:30
VLAI
EPSS
VEX
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)
Assigner
References
7 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| 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) |
guessed | |
| 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) |
guessed |
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"descriptions": [
{
"lang": "en",
"value": "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 ]"
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.5,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"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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"shortName": "Linux"
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{
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"title": "libceph: Reject monmaps advertising zero monitors",
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"cveId": "CVE-2026-68155",
"datePublished": "2026-08-10T11:59:21.200Z",
"dateReserved": "2026-07-30T09:28:09.371Z",
"dateUpdated": "2026-08-19T16:30:22.933Z",
"state": "PUBLISHED"
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"date": "2026-09-30",
"epss": "0.0068",
"percentile": "0.50563"
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"value": "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": "CVE-2026-68155",
"lastModified": "2026-08-19T17:20:32.680",
"metrics": {
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"attackVector": "NETWORK",
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"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
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"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-09-28T15:31:07+00:00",
"cve": "CVE-2026-68155",
"id": "CVE-2026-68155",
"initial_release_date": "2026-08-10T11:59:21.200000+00:00",
"product_status:fixed": "762",
"product_status:known_affected": "50",
"product_status:known_not_affected": "16",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: Linux kernel (libceph): Denial of Service due to malformed monitor maps",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-68155.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "important",
"current_release_date": "2026-09-28T23:50:03Z",
"cve": "CVE-2026-68155",
"id": "CVE-2026-68155",
"initial_release_date": "2026-08-18T00:08:30Z",
"product_status:first_fixed": "68",
"product_status:known_affected": "438",
"product_status:known_not_affected": "155",
"product_status:recommended": "351",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-68155",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-68155.json",
"version": "13"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
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.
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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.
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.
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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.
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