CyberSecBulletin
CVE-2026-68155NVD status: Received

In the Linux kernel, the following vulnerability has been resolved: libceph: Reject monmaps…

Published Updated By the CyberSecBulletin desk

CVE-2026-68155 is a high-severity improper input validation vulnerability in Linux, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions ba5f0015bfd376d764163045a61c17be75f44dae, caf082ef8609a6ac26159ce115f55ab7d00231a3, e3ccd4ecab09b22f507f49cb7ed9990c7158ceab as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.7% chance of exploitation within 30 days, higher than 54% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to ba5f0015bfd376d764163045a61c17be75f44dae or caf082ef8609a6ac26159ce115f55ab7d00231a3 or e3ccd4ecab09b22f507f49cb7ed9990c7158ceab or 0591a15815b498be628a937146e44487d599ba33, whichever matches your release line, or a later version.
  2. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxba75bb98cfb93b62c54af25bf67ff90857264bbe up to, but not including, ba5f0015bfd376d764163045a61c17be75f44dae; ba75bb98cfb93b62c54af25bf67ff90857264bbe up to, but not including, caf082ef8609a6ac26159ce115f55ab7d00231a3; ba75bb98cfb93b62c54af25bf67ff90857264bbe up to, but not including, e3ccd4ecab09b22f507f49cb7ed9990c7158ceab; ba75bb98cfb93b62c54af25bf67ff90857264bbe up to, but not including, 0591a15815b498be628a937146e44487d599ba33; ba75bb98cfb93b62c54af25bf67ff90857264bbe up to, but not including, cd0d41bc569632eaaeccde9d2a6bc919ec00c407; ba75bb98cfb93b62c54af25bf67ff90857264bbe up to, but not including, e67e8b694872c9bc66996040f9de9242f6236ed9; ba75bb98cfb93b62c54af25bf67ff90857264bbe up to, but not including, 3b249546f59c3d6d3592c10657f82bc3f1faa07c; ba75bb98cfb93b62c54af25bf67ff90857264bbe up to, but not including, 40480eee361ed9676b3f844d532ac28b47251634; and 1 more rangesba5f0015bfd376d764163045a61c17be75f44dae, caf082ef8609a6ac26159ce115f55ab7d00231a3, e3ccd4ecab09b22f507f49cb7ed9990c7158ceab, 0591a15815b498be628a937146e44487d599ba33, cd0d41bc569632eaaeccde9d2a6bc919ec00c407, e67e8b694872c9bc66996040f9de9242f6236ed9

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA.

Official 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 ]

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How developers prevent this class of flaw

  • Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses.
  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

More Improper Input Validation vulnerabilities (CWE-20)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Improper Input Validation vulnerabilities

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