CVE-2026-68155 (GCVE-0-2026-68155)
Vulnerability from cvelistv5
Published
2026-08-10 11:59
Modified
2026-08-19 16:30
Severity ?
VLAI Severity ?
EPSS score ?
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 ]
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: ba75bb98cfb93b62c54af25bf67ff90857264bbe Version: ba75bb98cfb93b62c54af25bf67ff90857264bbe Version: ba75bb98cfb93b62c54af25bf67ff90857264bbe Version: ba75bb98cfb93b62c54af25bf67ff90857264bbe Version: ba75bb98cfb93b62c54af25bf67ff90857264bbe Version: ba75bb98cfb93b62c54af25bf67ff90857264bbe Version: ba75bb98cfb93b62c54af25bf67ff90857264bbe |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/ceph/mon_client.c"
],
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{
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{
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"product": "Linux",
"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.34"
},
{
"lessThan": "2.6.34",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.216",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.148",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.101",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.42",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.6",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.15.216",
"versionStartIncluding": "2.6.34",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.183",
"versionStartIncluding": "2.6.34",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "2.6.34",
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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{
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"versionStartIncluding": "2.6.34",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"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."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-19T16:30:22.933Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/caf082ef8609a6ac26159ce115f55ab7d00231a3"
},
{
"url": "https://git.kernel.org/stable/c/e3ccd4ecab09b22f507f49cb7ed9990c7158ceab"
},
{
"url": "https://git.kernel.org/stable/c/0591a15815b498be628a937146e44487d599ba33"
},
{
"url": "https://git.kernel.org/stable/c/cd0d41bc569632eaaeccde9d2a6bc919ec00c407"
},
{
"url": "https://git.kernel.org/stable/c/e67e8b694872c9bc66996040f9de9242f6236ed9"
},
{
"url": "https://git.kernel.org/stable/c/3b249546f59c3d6d3592c10657f82bc3f1faa07c"
},
{
"url": "https://git.kernel.org/stable/c/40480eee361ed9676b3f844d532ac28b47251634"
}
],
"title": "libceph: Reject monmaps advertising zero monitors",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"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"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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