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 ]
References8
- git.kernel.org/stable/c/0591a15815b498be628a937146e44487d599ba33
- git.kernel.org/stable/c/3b249546f59c3d6d3592c10657f82bc3f1faa07c
- git.kernel.org/stable/c/40480eee361ed9676b3f844d532ac28b47251634
- git.kernel.org/stable/c/ba5f0015bfd376d764163045a61c17be75f44dae
- git.kernel.org/stable/c/caf082ef8609a6ac26159ce115f55ab7d00231a3
- git.kernel.org/stable/c/cd0d41bc569632eaaeccde9d2a6bc919ec00c407
- git.kernel.org/stable/c/e3ccd4ecab09b22f507f49cb7ed9990c7158ceab
- git.kernel.org/stable/c/e67e8b694872c9bc66996040f9de9242f6236ed9
Metrics
- CVSS 3.1
-
7.5
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS — exploit probability
- 1% percentile: 53 · as of 12 November 2026
- CWE
- CWE-20
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