CVE-2026-68155: In the Linux kernel, the following vulnerability has been resolved: libceph: Reject monmaps advertising zero monitors A message of type CEPH_MSG_MON...

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 ]

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 0591a15815b498be628a937146e44487d599ba33; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < cd0d41bc569632eaaeccde9d2a6bc919ec00c407; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < e67e8b694872c9bc66996040f9de9242f6236ed9; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 3b249546f59c3d6d3592c10657f82bc3f1faa07c; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 40480eee361ed9676b3f844d532ac28b47251634; < 6.6.148; < 6.12.101; < 6.18.42; < 7.1.6
Linux	Linux	All versions

References

Timeline

Published: Aug 10, 2026
Last Modified: Aug 10, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-68155?

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 ]

How severe is CVE-2026-68155?

Severity scoring for CVE-2026-68155 is pending analysis.

How do I fix CVE-2026-68155?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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