{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-80557","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-08-26T14:34:25.767Z","datePublished":"2026-08-26T14:37:24.178Z","dateUpdated":"2026-08-27T12:40:16.573Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-27T12:40:16.573Z"},"descriptions":[{"lang":"en","value":"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 ]"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - The bug is triggered when libceph decodes a crafted MOSDOpReply for CEPH_OSD_OP_LIST_WATCHERS received over the Ceph messenger TCP session from a compromised or malicious OSD; exploitation requires no local syscall, ioctl, or device access on the victim.\nAC:L - A malicious OSD fully controls the reply encoding and can set struct_len=0 with a chosen outdata_len so ceph_start_decoding() leaves p at end and the following ceph_decode_32() deterministically reads attacker-chosen bytes as num_watchers without races or victim-specific memory layout.\nPR:N - The attacker acts as the remote Ceph OSD peer and needs no account, capabilities, or privileges on the victim Linux host; any kernel RBD client connected to a multi-tenant or attacker-controlled cluster is exposed when exclusive-lock recovery issues LIST_WATCHERS.\nUI:N - Once an RBD image with exclusive-lock is mapped, ceph_osdc_list_watchers() is invoked automatically during rbd_try_lock() lock-contention recovery; no additional victim user or administrator action is required at exploit time beyond the existing client session.\nS:U - The out-of-bounds read, attacker-sized heap allocation, and any resulting kernel memory corruption all occur within the victim host kernel Ceph client; the flaw does not cross VM, container, or IOMMU security boundaries.\nC:H - The missing bounds check causes a 4-byte out-of-bounds kernel memory read via ceph_decode_32() when p equals end; per kernel guidance any out-of-bounds read is rated High, and the attacker can place controlled bytes immediately past the validated boundary via outdata_len.\nI:H - The out-of-bounds or attacker-supplied num_watchers value is passed directly to kzalloc_objs(), giving the remote peer control over kernel heap allocation size and subsequent decode_watchers() processing of watcher structures in the RBD exclusive-lock path.\nA:H - The slab out-of-bounds read can trigger KASAN faults or kernel oops on instrumented builds, and a large attacker-chosen num_watchers can cause ENOMEM/OOM or stall the RBD lock worker during repeated decode_watcher() attempts, producing severe repeatable availability loss."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ceph/osd_client.c"],"versions":[{"version":"a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c","lessThan":"85479b7d65b4ebcb07fbbe57230976793974ab4a","status":"affected","versionType":"git"},{"version":"a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c","lessThan":"1c824e7c75bb4adf19553dd4ea944a5d83096be8","status":"affected","versionType":"git"},{"version":"a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c","lessThan":"f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6","status":"affected","versionType":"git"},{"version":"a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c","lessThan":"eab3eeb68bfc639d74f27256f05546af5c4f787d","status":"affected","versionType":"git"},{"version":"a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c","lessThan":"c59219a6b62d74936963983e5815524c3de8dd79","status":"affected","versionType":"git"},{"version":"a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c","lessThan":"cb8246e5846dbbe34930903a90c7a90dd8e5910b","status":"affected","versionType":"git"},{"version":"a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c","lessThan":"7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1","status":"affected","versionType":"git"},{"version":"a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c","lessThan":"00ead17c7de137a692edee59f2772e6af687e8eb","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ceph/osd_client.c"],"versions":[{"version":"4.9","status":"affected"},{"version":"0","lessThan":"4.9","status":"unaffected","versionType":"semver"},{"version":"5.10.267","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.218","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.185","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.154","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.106","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.47","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.10","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"5.10.267"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"5.15.218"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"6.1.185"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"6.6.154"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"6.12.106"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"6.18.47"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"7.1.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9","versionEndExcluding":"7.2"}]}]}],"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"}],"title":"libceph: fix OOB read in decode_watchers() via missing bounds check","x_generator":{"engine":"bippy-1.2.0"}}}}