libceph: fix OOB read in decode_watchers() via missing bounds check

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-80557
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-26 15:17:10 UTC
Updated2026-08-27 13:18:40 UTC
DescriptionIn 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 ]

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c 85479b7d65b4ebcb07fbbe57230976793974ab4a git Not specified
CNA Linux Linux affected a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c 1c824e7c75bb4adf19553dd4ea944a5d83096be8 git Not specified
CNA Linux Linux affected a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6 git Not specified
CNA Linux Linux affected a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c eab3eeb68bfc639d74f27256f05546af5c4f787d git Not specified
CNA Linux Linux affected a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c c59219a6b62d74936963983e5815524c3de8dd79 git Not specified
CNA Linux Linux affected a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c cb8246e5846dbbe34930903a90c7a90dd8e5910b git Not specified
CNA Linux Linux affected a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c 7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1 git Not specified
CNA Linux Linux affected a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c 00ead17c7de137a692edee59f2772e6af687e8eb git Not specified
CNA Linux Linux affected 4.9 Not specified
CNA Linux Linux unaffected 4.9 semver Not specified
CNA Linux Linux unaffected 5.10.267 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.218 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.185 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.154 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.106 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.47 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.10 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/c59219a6b62d74936963983e5815524c3de8dd79 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cb8246e5846dbbe34930903a90c7a90dd8e5910b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/85479b7d65b4ebcb07fbbe57230976793974ab4a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1c824e7c75bb4adf19553dd4ea944a5d83096be8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/00ead17c7de137a692edee59f2772e6af687e8eb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/eab3eeb68bfc639d74f27256f05546af5c4f787d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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