CVE-2026-68155: Linux

High severity, CVSS 7.5. EPSS: 0.7% chance of exploitation in the next 30 days.

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 ]

Affected products

• Linux Linux: from 2.6.34, before 5.10.271 (fixed in 5.10.271); from 5.11, before 5.15.216 (fixed in 5.15.216); from 5.16, before 6.1.183 (fixed in 6.1.183); from 6.2, before 6.6.148 (fixed in 6.6.148); from 6.7, before 6.12.101 (fixed in 6.12.101); from 6.13, before 6.18.42 (fixed in 6.18.42); …

Published 2026-08-10. Last modified 2026-10-03.