CVE-2026-68155
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk46th percentile - higher than 46% of all known CVEs
Summary
In the Linux kernel's libceph module, a monmap with zero monitors was treated as valid, potentially leading to a client crash. The fix rejects such monmaps during decoding.
Risk Assessment
A corrupted monmap can cause a Ceph client crash, potentially leading to service unavailability.
Recommendation
Update the Linux kernel and filter messages from untrusted monitors.
Original NVD description (English source)
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 ]