CVE-2026-68155
Received Received - Intake

Reject Zero-Monitor Monmaps in Linux Kernel Ceph

Publication date: 2026-08-10

Last updated on: 2026-08-10

Assigner: kernel.org

Description
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 ]

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Meta Information

Published
2026-08-10
Last Modified
2026-08-10
Generated
2026-08-10
AI Q&A
2026-08-10
EPSS Evaluated
N/A
NVD
CVE-2026-68155
EUVD
EUVD-2026-55541

Affected Vendors & Products

Currently, no data is known.

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves the libceph component incorrectly accepting monmaps that advertise zero monitors. A monmap is a message containing cluster monitor information, and having zero monitors is impossible in a valid cluster. This malformed monmap can crash the client when it tries to open a session due to an assertion failure in the kernel code.

Detection Guidance

This vulnerability involves corrupted monmaps with zero monitors in Ceph clusters. Detection requires checking Ceph client logs for crashes or BUG_ON assertions in __open_session() or pick_new_mon(). Monitor logs should be inspected for malformed monmaps. No specific commands are provided in the context.

Impact Analysis

If exploited, this vulnerability could cause a system crash or denial of service by triggering a kernel assertion failure when processing a corrupted monmap. It primarily affects systems using the Ceph distributed storage system, potentially leading to service disruption or data access issues.

Mitigation Strategies

Apply the Linux kernel patch that rejects monmaps with num_mon == 0. Update Ceph clients to versions containing this fix. Monitor Ceph clusters for malformed monmaps and client crashes.

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