{"id":"CVE-2026-68082","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-68082","generatedAt":"2026-10-27T23:56:53.395Z","title":"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…","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nlibceph: fix two unsafe bare decodes in decode_lockers()\n\ndecode_lockers() in cls_lock_client.c contains two bare decode operations\nthat allow a malicious or compromised OSD to trigger slab-out-of-bounds\nreads:\n\n1. ceph_decode_32(p) at the num_lockers field has no preceding bounds\n   check. ceph_start_decoding() accepts struct_len=0 as valid -- the\n   internal ceph_decode_need(p, end, 0, bad) always passes -- so when an\n   OSD sends struct_len=0, ceph_start_decoding() returns success with\n   p == end. The immediately following bare ceph_decode_32(p) then reads\n   4 bytes past the validated buffer boundary. The garbage value is\n   passed directly to kzalloc_objs() as the locker count.\n\n   The sibling function decode_watchers() in osd_client.c already uses\n   ceph_decode_32_safe() after its own ceph_start_decoding() call.\n   decode_lockers() was the only site using the bare variant.\n\n2. ceph_decode_8(p) after the decode_locker() loop has no preceding\n   bounds check. If an OSD crafts num_lockers such that the loop\n   advances p exactly to end, the subsequent bare ceph_decode_8(p) reads\n   one byte past the validated buffer boundary. The result is passed\n   directly into *type, which is used as a lock type discriminator by\n   callers, giving an OSD-controlled one-byte OOB read with direct\n   influence over the lock type field.\n\nFix both by replacing bare operations with their safe variants:\n  ceph_decode_32(p) -> ceph_decode_32_safe(p, end, *num_lockers,\n                                           err_inval)\n  ceph_decode_8(p)  -> ceph_decode_8_safe(p, end, *type,\n                                          err_free_lockers)\n\nThe goto targets differ intentionally:\n  err_inval: is a new label returning -EINVAL directly. It is used for\n  the pre-allocation failure path where *lockers is not yet allocated\n  and must not be passed to ceph_free_lockers().\n\n  err_free_lockers: is the existing label. It is used for the\n  post-allocation failure path where *lockers is allocated and must\n  be freed.\n\nret is set to -EINVAL before ceph_decode_8_safe() so that\nerr_free_lockers returns the correct error code on bounds violation.\nWithout this, err_free_lockers would return a stale ret value (0 from\nthe successful decode_locker() loop), silently swallowing the error.\n\n-EINVAL is correct for both failure paths. The data received from the\nOSD is structurally malformed. -ENOMEM would misrepresent the failure\nclass to callers and to stable@ backporters triaging error paths.\n\nAttacker model: a malicious or compromised OSD in a multi-tenant Ceph\ndeployment can trigger this against any kernel client that issues the\nlock.get_info class method (e.g. during RBD exclusive lock acquisition).\n\n[ idryomov: trim changelog, formatting ]","published":"2026-08-08T10:16:55.000Z","lastModified":"2026-10-19T21:17:50.000Z","status":"Received","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-125"],"affected":[],"epss":{"score":0.00499,"percentile":0.4252,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.50%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/001835c599899ef1bd3506a815110a6374451554","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/02430f6f729b297e803d0605871f0a670b4eafd6","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/57ba829804fe6d34bbac3b826c4b15c1caa54862","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/7c422364acd93d7da1dfc27d6b54635a269653a1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/89df5d71f83f8e2781286798fd8ae5e42cf5f1a7","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a109a556115271ca7896dcda7b4b7e45e156c227","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a54be593d0b749161b08a1e56189b2cb9114267a","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c8ade01170a27d8ede0d761c255268af81e417f8","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-68082","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}