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NVD / CVE Program· CNA Linux

CVE-2026-80557: libceph: fix OOB read in decode_watchers() via missing bounds check

Noroxi assessment

Priority: Monitor (action score 39/100)

  • 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: 0.52% (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 00ead17c7de137a692edee59f2772e6af687e8eb, 1c824e7c75bb4adf19553dd4ea944a5d83096be8, 7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 00ead17c7de137a692edee59f2772e6af687e8eb, 1c824e7c75bb4adf19553dd4ea944a5d83096be8, 7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1 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: fix OOB read in decode_watchers() via missing bounds check ceph_start_decoding() validates that struct_len bytes remain in the buffer after the encoding header, but accepts struct_len=0 as valid: ceph_decode_need(p, end, 0, bad) always passes. When a malicious or compromised OSD sends an obj_list_watch_response_t reply with struct_len=0, ceph_start_decoding() returns success with p == end, leaving zero bytes guaranteed for subsequent reads. The immediately following ceph_decode_32(p) in decode_watchers() has no preceding bounds check. With p == end this is a 4-byte read past the validated buffer boundary. The garbage value is then passed directly to kzalloc_objs() as the watcher count. The sibling function decode_watcher() already uses the safe variants (ceph_decode_copy_safe, ceph_decode_64_safe, ceph_decode_skip_32) after its own ceph_start_decoding() call. decode_watchers() is the only site that uses the bare variant, confirming an oversight. Fix by replacing ceph_decode_32(p) with ceph_decode_32_safe(p, end, *num_watchers, bad), consistent with the established pattern. Attacker model: a malicious or compromised OSD in a multi-tenant Ceph deployment (e.g. cloud) can trigger this against any kernel client that calls CEPH_OSD_OP_LIST_WATCHERS, without any further privileges beyond OSD session establishment. [ idryomov: trim changelog ]

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Aug 26, 2026
Updated
Oct 16, 2026
EPSS
0.5% · 44th percentile
CWE
—

Report tools

JSON

Action score

39

Monitor

Low priority for now.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
9.8
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.

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

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When you'll hear from us

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  • when exploit code appears or is weaponized
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  • 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.

—

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

    • 4.9affected
    • a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and later · before 85479b7d65b4ebcb07fbbe57230976793974ab4aaffected · git
    • a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and later · before 1c824e7c75bb4adf19553dd4ea944a5d83096be8affected · git
    • a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and later · before f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6affected · git
    • a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and later · before eab3eeb68bfc639d74f27256f05546af5c4f787daffected · git
    • a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and later · before c59219a6b62d74936963983e5815524c3de8dd79affected · git
    • a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and later · before cb8246e5846dbbe34930903a90c7a90dd8e5910baffected · git
    • a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and later · before 7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1affected · git
    • a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and later · before 00ead17c7de137a692edee59f2772e6af687e8ebaffected · git
    • before 4.9not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.187-16.1.187-1
Debian:12linux-6.12before 6.12.107-1~deb12u16.12.107-1~deb12u1
Debian:13linuxbefore 6.12.107-16.12.107-1
Debian:14linuxbefore 7.1.10-17.1.10-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-80553Aug 26, 2026 · s390/vfio_ccw: Cancel existing workqueues
    35Monitor
  • ← EarlierCVE-2026-80554Aug 26, 2026 · s390/vfio_ccw: Limit the number of channel program segments
    37Monitor
  • Later →CVE-2026-80558Aug 26, 2026 · libceph: Avoid using invalid osd indices from primary_temp
    39Monitor

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 Linux00ead17c7de137a692edee59f2772e6af687e8ebVendor (CNA)
Linux Linux1c824e7c75bb4adf19553dd4ea944a5d83096be8Vendor (CNA)
Linux Linux7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1Vendor (CNA)
Linux Linux85479b7d65b4ebcb07fbbe57230976793974ab4aVendor (CNA)
Linux Linuxc59219a6b62d74936963983e5815524c3de8dd79Vendor (CNA)
Linux Linuxcb8246e5846dbbe34930903a90c7a90dd8e5910bVendor (CNA)
Linux Linuxeab3eeb68bfc639d74f27256f05546af5c4f787dVendor (CNA)
Linux Linuxf161be39201eb5f9b1f58fb8f90b8a9cd3931eb6Vendor (CNA)
debian:linux6.1.187-1 · Debian:12Package registry (OSV)
debian:linux-6.126.12.107-1~deb12u1 · 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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

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.

No nightly-computed relations.

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

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 (7 more)

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

All records