{"id":"CVE-2026-80557","title":"libceph: fix OOB read in decode_watchers() via missing bounds check","summary":"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 heade…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < 85479b7d65b4ebcb07fbbe57230976793974ab4a","Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < 1c824e7c75bb4adf19553dd4ea944a5d83096be8","Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6","Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < eab3eeb68bfc639d74f27256f05546af5c4f787d","Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < c59219a6b62d74936963983e5815524c3de8dd79","Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < cb8246e5846dbbe34930903a90c7a90dd8e5910b","Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < 7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1","Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < 00ead17c7de137a692edee59f2772e6af687e8eb","Linux 4.9"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"total","timestamp":"2026-10-16T19:17:25.527528Z"},"published":"2026-08-26","updated":"2026-10-16","sourceUpdated":"2026-10-16T19:26:26.946Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-80557","references":[{"url":"https://git.kernel.org/stable/c/85479b7d65b4ebcb07fbbe57230976793974ab4a"},{"url":"https://git.kernel.org/stable/c/1c824e7c75bb4adf19553dd4ea944a5d83096be8"},{"url":"https://git.kernel.org/stable/c/f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6"},{"url":"https://git.kernel.org/stable/c/eab3eeb68bfc639d74f27256f05546af5c4f787d"},{"url":"https://git.kernel.org/stable/c/c59219a6b62d74936963983e5815524c3de8dd79"},{"url":"https://git.kernel.org/stable/c/cb8246e5846dbbe34930903a90c7a90dd8e5910b"},{"url":"https://git.kernel.org/stable/c/7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1"},{"url":"https://git.kernel.org/stable/c/00ead17c7de137a692edee59f2772e6af687e8eb"}],"tags":["cve.org"],"epss":0.00525,"epssPercentile":0.43268,"ingestedAt":"2026-10-16T19:46:24.315Z","slug":"CVE-2026-80557","body":"## Overview\n\nIn 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 ]\n\n## Affected\n\n- `Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < 85479b7d65b4ebcb07fbbe57230976793974ab4a`\n- `Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < 1c824e7c75bb4adf19553dd4ea944a5d83096be8`\n- `Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6`\n- `Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < eab3eeb68bfc639d74f27256f05546af5c4f787d`\n- `Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < c59219a6b62d74936963983e5815524c3de8dd79`\n- `Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < cb8246e5846dbbe34930903a90c7a90dd8e5910b`\n- `Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < 7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1`\n- `Linux >= a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c < 00ead17c7de137a692edee59f2772e6af687e8eb`\n- `Linux 4.9`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}