{"id":"CVE-2026-89682","state":"PUBLISHED","title":"nfsd: fix fcache_disposal UAF by inlining dispose state into nfsd_net","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix fcache_disposal UAF by inlining dispose state into nfsd_net\n\nnfsd_file_dispose_list_delayed() defers fput() to nfsd service threads\nvia a per-net freeme queue, preventing the shrinker and GC worker from\nbearing the cost of closing files (see ffb402596147).  However, the\nqueue lives in a separately-allocated struct nfsd_fcache_disposal that\nis freed by nfsd_free_fcache_disposal_net() during per-net teardown.\nThe global shrinker, laundrette, and fsnotify callbacks can still be\ninside nfsd_file_dispose_list_delayed() dereferencing that pointer,\ncausing a use-after-free.\n\nInline the spinlock and freeme list directly into struct nfsd_net (as\nfcache_dispose_lock and fcache_dispose_list), eliminating the separately\nallocated struct nfsd_fcache_disposal entirely.  These fields now have\nthe same lifetime as the net namespace itself, so there is no dangling\npointer to chase.\n\nnfsd_file_cache_start_net() now just initializes the inline fields and\ncannot fail due to allocation.  nfsd_file_cache_shutdown_net() drains\nthe inline list directly instead of freeing a separate struct.  The\nalloc/free helpers are removed.","publishedAt":"2026-09-11T19:46:04.882Z","updatedAt":"2026-10-30T12:32:40.915Z","severity":{"score":8.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"41fe0e804bbf1110c0aba2ebdfc729efb240d8a6","versionType":"git"},{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"e6c3a43d0a41f03abae3764fc82a59369360c7e0","versionType":"git"},{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"9c8ac7c2b9b150e13b7ad0d0fae54f17747dce67","versionType":"git"},{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"ba0ee9e04b7a0356c28d5a2fe445db675d24e572","versionType":"git"},{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"cadc9036d5a8209f89e7026ddba7cfb1c716b03c","versionType":"git"},{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4","versionType":"git"},{"version":"e8f923e1e9fcc0832a12c8a2461792e5a9544c03","status":"affected","versionType":"git"},{"version":"3bc94fb44f10ef852723e1aeaac6794c5ab16aec","status":"affected","versionType":"git"},{"version":"5.10.220","status":"affected","lessThan":"5.11","versionType":"semver"},{"version":"5.15.154","status":"affected","lessThan":"5.16","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/filecache.c","fs/nfsd/netns.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.17","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.51","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/filecache.c","fs/nfsd/netns.h"]}],"references":["https://git.kernel.org/stable/c/41fe0e804bbf1110c0aba2ebdfc729efb240d8a6","https://git.kernel.org/stable/c/e6c3a43d0a41f03abae3764fc82a59369360c7e0","https://git.kernel.org/stable/c/9c8ac7c2b9b150e13b7ad0d0fae54f17747dce67","https://git.kernel.org/stable/c/ba0ee9e04b7a0356c28d5a2fe445db675d24e572","https://git.kernel.org/stable/c/cadc9036d5a8209f89e7026ddba7cfb1c716b03c","https://git.kernel.org/stable/c/bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4"],"weaknesses":[],"ingestedAt":"2026-10-30T12:52:04.348Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/89xxx/CVE-2026-89682.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89682","state":"PUBLISHED","datePublished":"2026-09-11T19:46:04.882Z","dateUpdated":"2026-10-30T12:32:40.915Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.748Z"},"containers":{"cna":{"title":"nfsd: fix fcache_disposal UAF by inlining dispose state into nfsd_net","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix fcache_disposal UAF by inlining dispose state into nfsd_net\n\nnfsd_file_dispose_list_delayed() defers fput() to nfsd service threads\nvia a per-net freeme queue, preventing the shrinker and GC worker from\nbearing the cost of closing files (see ffb402596147).  However, the\nqueue lives in a separately-allocated struct nfsd_fcache_disposal that\nis freed by nfsd_free_fcache_disposal_net() during per-net teardown.\nThe global shrinker, laundrette, and fsnotify callbacks can still be\ninside nfsd_file_dispose_list_delayed() dereferencing that pointer,\ncausing a use-after-free.\n\nInline the spinlock and freeme list directly into struct nfsd_net (as\nfcache_dispose_lock and fcache_dispose_list), eliminating the separately\nallocated struct nfsd_fcache_disposal entirely.  These fields now have\nthe same lifetime as the net namespace itself, so there is no dangling\npointer to chase.\n\nnfsd_file_cache_start_net() now just initializes the inline fields and\ncannot fail due to allocation.  nfsd_file_cache_shutdown_net() drains\nthe inline list directly instead of freeing a separate struct.  The\nalloc/free helpers are removed."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"41fe0e804bbf1110c0aba2ebdfc729efb240d8a6","versionType":"git"},{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"e6c3a43d0a41f03abae3764fc82a59369360c7e0","versionType":"git"},{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"9c8ac7c2b9b150e13b7ad0d0fae54f17747dce67","versionType":"git"},{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"ba0ee9e04b7a0356c28d5a2fe445db675d24e572","versionType":"git"},{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"cadc9036d5a8209f89e7026ddba7cfb1c716b03c","versionType":"git"},{"version":"1463b38e7cf34d4cc60f41daff459ad807b2e408","status":"affected","lessThan":"bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4","versionType":"git"},{"version":"e8f923e1e9fcc0832a12c8a2461792e5a9544c03","status":"affected","versionType":"git"},{"version":"3bc94fb44f10ef852723e1aeaac6794c5ab16aec","status":"affected","versionType":"git"},{"version":"5.10.220","status":"affected","lessThan":"5.11","versionType":"semver"},{"version":"5.15.154","status":"affected","lessThan":"5.16","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/filecache.c","fs/nfsd/netns.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.17","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.51","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/filecache.c","fs/nfsd/netns.h"]}],"references":[{"url":"https://git.kernel.org/stable/c/41fe0e804bbf1110c0aba2ebdfc729efb240d8a6"},{"url":"https://git.kernel.org/stable/c/e6c3a43d0a41f03abae3764fc82a59369360c7e0"},{"url":"https://git.kernel.org/stable/c/9c8ac7c2b9b150e13b7ad0d0fae54f17747dce67"},{"url":"https://git.kernel.org/stable/c/ba0ee9e04b7a0356c28d5a2fe445db675d24e572"},{"url":"https://git.kernel.org/stable/c/cadc9036d5a8209f89e7026ddba7cfb1c716b03c"},{"url":"https://git.kernel.org/stable/c/bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.1,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - nfsd_file_dispose_list_delayed() runs in the in-kernel NFS server filecache on nfsd_files cached from remote OPEN/READ/WRITE over TCP/UDP 2049; a network NFS client populates that cache and can drive delayed dispose via the global GC laundrette, shrinker, or fsnotify from REMOVE, matching kernel guidance that nfsd is Network.\nAC:H - The UAF requires nfsd_free_fcache_disposal_net() to kfree the separately allocated per-net nfsd_fcache_disposal during nfsd_file_cache_shutdown_net() while the global shrinker, laundrette, or fsnotify still dereference it—a victim-side nfsd restart, shutdown, or netns teardown the remote attacker cannot cause, only race against.\nPR:N - Typical nfsd deployments use AUTH_SYS/AUTH_NULL with IP-based exports, so a remote peer that can reach the export self-asserts credentials with no cryptographic authentication and can OPEN/READ files into the filecache; no local Linux account or capability is required.\nUI:N - The attacker issues NFS operations that populate and reclaim the filecache themselves; nfsd per-net teardown is an environmental race counted under Attack Complexity, not an interactive victim action such as mounting a filesystem or opening a file.\nS:U - The use-after-free corrupts host-kernel slab (struct nfsd_fcache_disposal) within the same OS security authority as nfsd and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - This is a slab use-after-free of the kmalloc'd nfsd_fcache_disposal object; reclaim or spray of the freed object lets dispose_list_delayed read attacker-controlled lock and list_head fields, enabling arbitrary kernel disclosure per UAF guidance.\nI:H - spin_lock and list_move_tail on the freed disposal object write into reclaimed slab, corrupting list nodes and lock state and yielding a groomable write or control-flow hijack primitive characteristic of exploitable kernel UAFs.\nA:H - Use-after-free of the disposal spinlock and list from shrinker, GC worker, or fsnotify context causes kernel oops, panic, or list-corruption hangs, fully disrupting availability of the NFS server host."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:32:40.915Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.18.51"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"7.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10.220"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.154"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}