{"id":"CVE-2026-80557","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-80557","summary":"libceph: fix OOB read in decode_watchers() via missing bounds check","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nlibceph: fix OOB read in decode_watchers() via missing bounds check\n\nceph_start_decoding() validates that struct_len bytes remain in the\nbuffer after the encoding header, but accepts struct_len=0 as valid:\nceph_decode_need(p, end, 0, bad) always passes. When a malicious or\ncompromised OSD sends an obj_list_watch_response_t reply with\nstruct_len=0, ceph_start_decoding() returns success with p == end,\nleaving zero bytes guaranteed for subsequent reads.\n\nThe immediately following ceph_decode_32(p) in decode_watchers() has\nno preceding bounds check. With p == end this is a 4-byte read past\nthe validated buffer boundary. The garbage value is then passed\ndirectly to kzalloc_objs() as the watcher count.\n\nThe sibling function decode_watcher() already uses the safe variants\n(ceph_decode_copy_safe, ceph_decode_64_safe, ceph_decode_skip_32)\nafter its own ceph_start_decoding() call. decode_watchers() is the\nonly site that uses the bare variant, confirming an oversight.\n\nFix by replacing ceph_decode_32(p) with ceph_decode_32_safe(p, end,\n*num_watchers, bad), consistent with the established pattern.\n\nAttacker model: a malicious or compromised OSD in a multi-tenant Ceph\ndeployment (e.g. cloud) can trigger this against any kernel client\nthat calls CEPH_OSD_OP_LIST_WATCHERS, without any further privileges\nbeyond OSD session establishment.\n\n[ idryomov: trim changelog ]","published":"2026-08-26T14:37:24.178Z","modified":"2026-08-28T03:47:29.010363471Z","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":{"score":0.00379,"percentile":0.30803,"asOf":"2026-08-27"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"5.10.267"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/00ead17c7de137a692edee59f2772e6af687e8eb"},{"type":"WEB","url":"https://git.kernel.org/stable/c/1c824e7c75bb4adf19553dd4ea944a5d83096be8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/85479b7d65b4ebcb07fbbe57230976793974ab4a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c59219a6b62d74936963983e5815524c3de8dd79"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cb8246e5846dbbe34930903a90c7a90dd8e5910b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/eab3eeb68bfc639d74f27256f05546af5c4f787d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80557.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-80557"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-28T03:47:29.010363471Z"}}