Critical

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

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 ]

Published Aug 26, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (critical)+10

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.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Linux

CVSS base

9.8

Critical · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

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).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and < 85479b7d65b4ebcb07fbbe57230976793974ab4a≥ a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and < 1c824e7c75bb4adf19553dd4ea944a5d83096be8≥ a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and < f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6≥ a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and < eab3eeb68bfc639d74f27256f05546af5c4f787d≥ a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and < c59219a6b62d74936963983e5815524c3de8dd79≥ a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and < cb8246e5846dbbe34930903a90c7a90dd8e5910b≥ a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and < 7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1≥ a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c and < 00ead17c7de137a692edee59f2772e6af687e8eb and 1 more version 4.9	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

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
9.8	CVSS 3.1	Critical	3.9	5.9	416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database
9.8	CVSS 3.1	Critical	—	—	Linux via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67)

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).

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 15, 2026
CVSS changed · 9.8
Oct 15, 2026 · NIST National Vulnerability Database
Source status changed · → Received
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Aug 26, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

8 on the record

git.kernel.org/stable/c/1c824e7c75bb4adf19553dd4ea944a5d83096be8
NIST National Vulnerability Database
git.kernel.org/stable/c/00ead17c7de137a692edee59f2772e6af687e8eb
NIST National Vulnerability Database
git.kernel.org/stable/c/cb8246e5846dbbe34930903a90c7a90dd8e5910b
NIST National Vulnerability Database
git.kernel.org/stable/c/85479b7d65b4ebcb07fbbe57230976793974ab4a
NIST National Vulnerability Database
git.kernel.org/stable/c/7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1
NIST National Vulnerability Database
git.kernel.org/stable/c/f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6
NIST National Vulnerability Database
git.kernel.org/stable/c/c59219a6b62d74936963983e5815524c3de8dd79
NIST National Vulnerability Database
git.kernel.org/stable/c/eab3eeb68bfc639d74f27256f05546af5c4f787d
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 11h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 11h
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 FIRST EPSS score.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
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-2026-80557 is "libceph: fix OOB read in decode_watchers() via missing bounds check", rated Critical. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.8 describes technical severity. 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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