CVE-2026-68082libceph: fix two unsafe bare decodes in decode_lockers()

Description

In the Linux kernel, the following vulnerability has been resolved: libceph: fix two unsafe bare decodes in decode_lockers() decode_lockers() in cls_lock_client.c contains two bare decode operations that allow a malicious or compromised OSD to trigger slab-out-of-bounds reads: 1. ceph_decode_32(p) at the num_lockers field has no preceding bounds check. ceph_start_decoding() accepts struct_len=0 as valid -- the internal ceph_decode_need(p, end, 0, bad) always passes -- so when an OSD sends struct_len=0, ceph_start_decoding() returns success with p == end. The immediately following bare ceph_decode_32(p) then reads 4 bytes past the validated buffer boundary. The garbage value is passed directly to kzalloc_objs() as the locker count. The sibling function decode_watchers() in osd_client.c already uses ceph_decode_32_safe() after its own ceph_start_decoding() call. decode_lockers() was the only site using the bare variant. 2. ceph_decode_8(p) after the decode_locker() loop has no preceding bounds check. If an OSD crafts num_lockers such that the loop advances p exactly to end, the subsequent bare ceph_decode_8(p) reads one byte past the validated buffer boundary. The result is passed directly into *type, which is used as a lock type discriminator by callers, giving an OSD-controlled one-byte OOB read with direct influence over the lock type field. Fix both by replacing bare operations with their safe variants: ceph_decode_32(p) -> ceph_decode_32_safe(p, end, *num_lockers, err_inval) ceph_decode_8(p) -> ceph_decode_8_safe(p, end, *type, err_free_lockers) The goto targets differ intentionally: err_inval: is a new label returning -EINVAL directly. It is used for the pre-allocation failure path where *lockers is not yet allocated and must not be passed to ceph_free_lockers(). err_free_lockers: is the existing label. It is used for the post-allocation failure path where *lockers is allocated and must be freed. ret is set to -EINVAL before ceph_decode_8_safe() so that err_free_lockers returns the correct error code on bounds violation. Without this, err_free_lockers would return a stale ret value (0 from the successful decode_locker() loop), silently swallowing the error. -EINVAL is correct for both failure paths. The data received from the OSD is structurally malformed. -ENOMEM would misrepresent the failure class to callers and to stable@ backporters triaging error paths. Attacker model: a malicious or compromised OSD in a multi-tenant Ceph deployment can trigger this against any kernel client that issues the lock.get_info class method (e.g. during RBD exclusive lock acquisition). [ idryomov: trim changelog, formatting ]

Timeline

Scores

EPSS (exploitation in 30 days)

0.50% · top 57% of all CVEs (13 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: yes · Technical impact: total

The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.

Affected products

• Linux · Linux

  • affected d4ed4a530562881cc5225050e42d96034f405aae – < c8ade01170a27d8ede0d761c255268af81e417f8
  • affected d4ed4a530562881cc5225050e42d96034f405aae – < 001835c599899ef1bd3506a815110a6374451554
  • affected d4ed4a530562881cc5225050e42d96034f405aae – < 7c422364acd93d7da1dfc27d6b54635a269653a1
  • affected d4ed4a530562881cc5225050e42d96034f405aae – < 02430f6f729b297e803d0605871f0a670b4eafd6
  • affected d4ed4a530562881cc5225050e42d96034f405aae – < 57ba829804fe6d34bbac3b826c4b15c1caa54862
  • affected d4ed4a530562881cc5225050e42d96034f405aae – < 89df5d71f83f8e2781286798fd8ae5e42cf5f1a7
  • affected d4ed4a530562881cc5225050e42d96034f405aae – < a54be593d0b749161b08a1e56189b2cb9114267a
  • affected d4ed4a530562881cc5225050e42d96034f405aae – < a109a556115271ca7896dcda7b4b7e45e156c227

• Linux · Linux

  • affected 4.9
  • unaffected < 4.9
  • unaffected 5.10.266 – ≤ 5.10.*
  • unaffected 5.15.217 – ≤ 5.15.*
  • unaffected 6.1.184 – ≤ 6.1.*
  • unaffected 6.6.153 – ≤ 6.6.*
  • unaffected 6.12.105 – ≤ 6.12.*
  • unaffected 6.18.46 – ≤ 6.18.*
  • unaffected 7.1.6 – ≤ 7.1.*
  • unaffected 7.2 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-54775 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-68082](https://cveledger.app/badge/CVE-2026-68082.svg)](https://cveledger.app/cve/CVE-2026-68082)

Record last updated 19 Oct 2026, 20:48 UTC.