{"id":"CVE-2026-68082","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-68082","summary":"libceph: fix two unsafe bare decodes in decode_lockers()","details":"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":"2026-08-08T09:17:45.394Z","modified":"2026-08-14T10:42:17.732480856Z","cvss":{"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"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"7.1.6"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/a109a556115271ca7896dcda7b4b7e45e156c227"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a54be593d0b749161b08a1e56189b2cb9114267a"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68082.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68082"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-14T10:42:17.732480856Z"}}