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NVD / CVE Program· CNA Linux

CVE-2026-43405: libceph: Use u32 for non-negative values in ceph_monmap_decode()

Noroxi assessment

Priority: Monitor (action score 30/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.59% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Linux Linux 08bc6173fd611ad5a40f472bf5f15b92aea0fe40, 5f2806684b05bd24d05c091083b8e2517ba8ffac, 770444611f047dbfd4517ec0bc1b179d40c2f346.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 08bc6173fd611ad5a40f472bf5f15b92aea0fe40, 5f2806684b05bd24d05c091083b8e2517ba8ffac, 770444611f047dbfd4517ec0bc1b179d40c2f346 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
May 8, 2026
Updated
Oct 19, 2026
EPSS
0.5% · 48th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
7.5
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-43405

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel5.11 and later · before 5.15.203
  • linux linux kernel5.16 and later · before 6.1.167
  • linux linux kernel6.2 and later · before 6.6.130
  • linux linux kernel6.7 and later · before 6.12.78
  • linux linux kernel6.13 and later · before 6.18.19
  • linux linux kernel6.19 and later · before 6.19.9
  • linux linux kernel7.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 5.11affected
    • a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and later · before ee5588e2bc41acb73f6676c0520420c107cd0140affected · git
    • a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and later · before 86f7060cd638d6eb042e8ed780fb83a59ca0dcb3affected · git
    • a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and later · before 5f2806684b05bd24d05c091083b8e2517ba8ffacaffected · git
    • a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and later · before b268984ae88cb0dcd7a8e8263962c748448e26e8affected · git
    • a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and later · before ba0a4df8c563536857dcbf7b4dbd0f2a15f57aceaffected · git
    • a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and later · before 08bc6173fd611ad5a40f472bf5f15b92aea0fe40affected · git
    • a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c and later · before 770444611f047dbfd4517ec0bc1b179d40c2f346affected · git
    • before 5.11not affected · semver
    • 5.15.203 and later · up to and including 5.15.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.170-16.1.170-1
Debian:13linuxbefore 6.12.85-16.12.85-1
Debian:14linuxbefore 6.19.10-16.19.10-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2026-43401May 8, 2026 · cpufreq: intel_pstate: Fix NULL pointer dereference in update_cpu_qos_request()
    22Monitor
  • ← EarlierCVE-2026-43402May 8, 2026 · kthread: consolidate kthread exit paths to prevent use-after-free
    39Monitor
  • Later →CVE-2026-43406May 8, 2026 · libceph: prevent potential out-of-bounds reads in process_message_header()
    36Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux08bc6173fd611ad5a40f472bf5f15b92aea0fe40Vendor (CNA)
Linux Linux5f2806684b05bd24d05c091083b8e2517ba8ffacVendor (CNA)
Linux Linux770444611f047dbfd4517ec0bc1b179d40c2f346Vendor (CNA)
Linux Linux86f7060cd638d6eb042e8ed780fb83a59ca0dcb3Vendor (CNA)
Linux Linuxb268984ae88cb0dcd7a8e8263962c748448e26e8Vendor (CNA)
Linux Linuxba0a4df8c563536857dcbf7b4dbd0f2a15f57aceVendor (CNA)
Linux Linuxee5588e2bc41acb73f6676c0520420c107cd0140Vendor (CNA)
debian:linux6.1.170-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2024-50302535 days apartHID: core: zero-initialize the report bufferKEV
    52Plan
  • CVE-2026-5298947 days apartnvmet-tcp: propagate nvmet_tcp_build_pdu_iovec() errors to its callers
    39Monitor
  • CVE-2026-5322548 days apartsctp: fix uninit-value in __sctp_rcv_asconf_lookup()
    36Monitor
  • CVE-2026-5317048 days apartaccel/ethosu: reject DMA commands with uninitialized length
    35Monitor
  • CVE-2026-431392 days apartxfrm6: fix uninitialized saddr in xfrm6_get_saddr()
    34Monitor
  • CVE-2026-432910 days apartnet: nfc: nci: Fix parameter validation for packet data
    33Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-908 · Use of Uninitialized Resource

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records