CVE-2026-43405 — libceph: Use u32 for non-negative values in ceph_monmap_decode()
In the Linux kernel, the following vulnerability has been resolved: libceph: Use u32 for non-negative values in ceph_monmap_decode() This patch fixes unnecessary implicit conversions that change signedness of blob_len and num_mon in ceph_monmap_decode(). Currently blob_len and num_mon are (signed) int variables. They are used to hold values that are always non-negative and get assigned in ceph_decode_32_safe(), which is meant to assign u32 values. Both variables are subsequently used as unsigned values, and the value of num_mon is further assigned to monmap->num_mon, which is of type u32. Therefore, both variables should be of type u32. This is especially relevant for num_mon. If the value read from the incoming message is very large, it is interpreted as a negative value, and the check for num_mon > CEPH_MAX_MON does not catch it. This leads to the attempt to allocate a very large chunk of memory for monmap, which will most likely fail. In this case, an unnecessary attempt to allocate memory is performed, and -ENOMEM is returned instead of -EINVAL.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.7% (30-day exploitation probability)+8
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the fixed version or the patch documented under Remediation.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux | version 5.11≥ a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and < 770444611f047dbfd4517ec0bc1b179d40c2f346≥ a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and < 08bc6173fd611ad5a40f472bf5f15b92aea0fe40≥ a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and < ba0a4df8c563536857dcbf7b4dbd0f2a15f57ace≥ a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and < b268984ae88cb0dcd7a8e8263962c748448e26e8≥ a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and < 5f2806684b05bd24d05c091083b8e2517ba8ffac≥ a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and < 86f7060cd638d6eb042e8ed780fb83a59ca0dcb3≥ a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and < ee5588e2bc41acb73f6676c0520420c107cd0140 | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Linux | Linux Kernel |
version 7.0-rc3≥ 5.11 and < 5.15.203version 7.0-rc2version 7.0-rc1≥ 6.19 and < 6.19.9≥ 6.13 and < 6.18.19≥ 6.7 and < 6.12.78≥ 6.2 and < 6.6.130 and 1 more≥ 5.16 and < 6.1.167 |
Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 7.5 | CVSS 3.1 | High | 3.9 | 3.6 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database |
| 7.5 | CVSS 3.1 | High | — | — | Linux via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.70%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · linux/linux
- Record published
- Fix documented
- CVSS changed · 7.5
- Source status changed · → Analyzed
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
7 on the record
- git.kernel.org/stable/c/08bc6173fd611ad5a40f472bf5f15b92aea0fe40
- git.kernel.org/stable/c/86f7060cd638d6eb042e8ed780fb83a59ca0dcb3
- git.kernel.org/stable/c/770444611f047dbfd4517ec0bc1b179d40c2f346
- git.kernel.org/stable/c/ee5588e2bc41acb73f6676c0520420c107cd0140
- git.kernel.org/stable/c/5f2806684b05bd24d05c091083b8e2517ba8ffac
- git.kernel.org/stable/c/b268984ae88cb0dcd7a8e8263962c748448e26e8
- git.kernel.org/stable/c/ba0a4df8c563536857dcbf7b4dbd0f2a15f57ace
Elsewhere on this site
Related CVEs (same products)
- Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 10h
- Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 10h
- Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
- Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
- Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
- Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No CISA SSVC assessment.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-43405 is "libceph: Use u32 for non-negative values in ceph_monmap_decode()", rated High. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. EPSS 0.70% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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