{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89692", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.749Z", "datePublished": "2026-09-11T19:46:12.040Z", "dateUpdated": "2026-10-19T08:51:05.555Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:51:05.555Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: clear CALLBACK_RUNNING on failed delegation recall queue\n\nnfsd_break_one_deleg() sets NFSD4_CALLBACK_RUNNING via test_and_set_bit\nat entry to serialize recall work, then calls nfsd4_run_cb() to queue\nthe recall. When the queue attempt fails the refcount bump is undone,\nbut the RUNNING bit is left set. The only site that clears the bit is\nnfsd41_destroy_cb() (fs/nfsd/nfs4callback.c), which runs from the\nworkqueue and is therefore unreachable when nothing was queued.\n\nThe bit becomes a permanent latch on dp->dl_recall.cb_flags: every\nsubsequent break_lease() on the same delegation hits the early-return\nguard in nfsd_break_one_deleg() and silently skips the recall, so the\ndelegation is never broken and the conflicting open or lock stalls.\n\nFix by clearing NFSD4_CALLBACK_RUNNING on the !queued branch alongside\nthe refcount_dec." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - nfsd_break_one_deleg() runs in in-kernel nfsd (fs/nfsd/nfs4state.c) and is reached over TCP/2049 via svc_process to nfsd_dispatch to nfsd4_proc_compound: a remote NFSv4 OPEN grants a delegation, then a conflicting OPEN hits nfsd_file_acquire/nfsd_open_break_lease to __break_lease to nfsd_break_deleg_cb().\nAC:L - The attacker drives both sides with two NFSv4 clients: one holds the delegation while the other sends conflicting OPEN/LOCK/SETATTR to invoke nfsd_break_one_deleg(), and can DESTROY_CLIENTID or flap the backchannel so queue_work() fails; the sequence is retryable and needs no uninfluenced memory layout.\nPR:N - Default AUTH_SYS/AUTH_NULL nfsd exports do not cryptographically verify RPC credentials; any host allowed by the export can EXCHANGE_ID/SETCLIENTID, OPEN to receive a delegation, and issue a conflicting OPEN with no local Linux account or capability.\nUI:N - The attacking NFS clients send the OPEN, conflicting OPEN, and optional DESTROY_CLIENTID RPCs themselves; no victim user on the NFS server must mount a filesystem, open a file, or otherwise interact at attack time.\nS:U - The latched NFSD4_CALLBACK_RUNNING bit and stalled lease-break live in kernel nfsd/VFS state on the NFS server; this is not a VM, IOMMU, or sandbox boundary crossing.\nC:N - The bug only leaves NFSD4_CALLBACK_RUNNING set so later recalls are skipped; it does not read attacker-inaccessible kernel memory, leak pointers, or return extra data to the client.\nI:N - There is no use-after-free, out-of-bounds write, or other memory corruption, and conflicting writers are blocked rather than committing unauthorized file changes, so integrity is unaffected.\nA:H - When nfsd4_run_cb() fails, RUNNING stays set, later break_lease() skips CB_RECALL, nfsd4_cb_recall_prepare never queues the delegation on del_recall_lru, and fl_break_time is zeroed so VFS will not expire the lease; conflicting opens/locks then stall or retry NFS4ERR_JUKEBOX indefinitely, denying the file and NFS service." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/nfs4state.c" ], "versions": [ { "version": "1054e8ffc5c492f341bdf1888b882f1d163dd3d8", "lessThan": "b137930ee52e3ef38915a3511d4c070463b63a32", "status": "affected", "versionType": "git" }, { "version": "1054e8ffc5c492f341bdf1888b882f1d163dd3d8", "lessThan": "cb2d0c4d1b3d301d042ed61365eaa8cb0141a254", "status": "affected", "versionType": "git" }, { "version": "1054e8ffc5c492f341bdf1888b882f1d163dd3d8", "lessThan": "b036727d334b1b7cd4c1f1fba3b59ba93a6bbe96", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/nfs4state.c" ], "versions": [ { "version": "6.15", "status": "affected" }, { "version": "0", "lessThan": "6.15", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "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": "6.15", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/b137930ee52e3ef38915a3511d4c070463b63a32" }, { "url": "https://git.kernel.org/stable/c/cb2d0c4d1b3d301d042ed61365eaa8cb0141a254" }, { "url": "https://git.kernel.org/stable/c/b036727d334b1b7cd4c1f1fba3b59ba93a6bbe96" } ], "title": "nfsd: clear CALLBACK_RUNNING on failed delegation recall queue", "x_generator": { "engine": "bippy-1.2.0" } } } }