{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89688", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.749Z", "datePublished": "2026-09-11T19:46:09.322Z", "dateUpdated": "2026-10-19T08:51:01.558Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:51:01.558Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: drop the stateid, not the stateowner, on seqid_op replay retry\n\nIn nfs4_preprocess_seqid_op() the stateid is obtained from\nnfsd4_lookup_stateid(), which holds a reference on the nfs4_stid\n(sc_count) but takes no reference on the stateowner. openlockstateid()\nmerely casts that stid and likewise takes no reference.\n\nWhen nfsd4_cstate_assign_replay() returns -EAGAIN (the replay owner is\nbeing torn down, RP_UNHASHED) it has not taken a stateowner reference on\nthat path. The error handling nevertheless called\nnfs4_put_stateowner(stp->st_stateowner), dropping an so_count reference\nthe function never acquired -- risking a stateowner refcount underflow and\nuse-after-free -- while leaking the sc_count reference held on the stid.\nThe leaked stid reference can also stall a concurrent\nnfsd4_close_open_stateid() waiting for sc_count to drop.\n\nDrop the reference actually held -- the stid -- before retrying. The\nstateowner stays alive through the reference held by the stid. This mirrors\nthe open path in nfsd4_process_open1(), where the put balances a reference\nthat path explicitly holds on the stateowner." } ], "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 - nfsd processes NFSv4 COMPOUND ops (CLOSE, OPEN_DOWNGRADE, LOCK, OPEN_CONFIRM) in the in-kernel NFS server on TCP/UDP 2049; those handlers call nfs4_preprocess_seqid_op(), so a remote peer reaches the bug with no local access.\nAC:L - A remote NFSv4.0 client drives both sides by sending concurrent CLOSE and another seqid-mutating op on the same openowner; CLOSE's move_to_close_lru() sets RP_UNHASHED and waits on sc_count, so the window is attacker-controlled and retryable.\nPR:N - Typical nfsd exports use AUTH_SYS/AUTH_NULL, so RPC uids are self-asserted and not cryptographically verified; any host allowed by the export list can SETCLIENTID, OPEN, then CLOSE/OPEN_DOWNGRADE with no local Linux account.\nUI:N - The attacker issues the NFSv4 COMPOUND requests itself; no victim on the server must mount a filesystem, open a file, or take any other action.\nS:U - The underflow frees an nfsd nfs4_stateowner in the NFS server kernel; impact stays in that kernel and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - nfs4_put_stateowner() drops an so_count the seqid path never took, freeing the stateowner while the stid and retry loop still use it; that UAF enables slab reclaim and kernel memory disclosure.\nI:H - The same UAF exposes so_ops->so_unhash/so_free function pointers and list writes under cl_lock, yielding a kernel write and control-flow hijack primitive.\nA:H - The UAF oopses or panics nfsd; the leaked stid sc_count also leaves move_to_close_lru() waiting forever for sc_count==2, hanging an nfsd thread, and the -EAGAIN retry can spin while RP_UNHASHED stays set." } ] } ], "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": "eec7620800081e27dbf8019ac2e66259f0d5bf6f", "lessThan": "69ed78b6b947c9257213164678b4edf17533093b", "status": "affected", "versionType": "git" }, { "version": "eec7620800081e27dbf8019ac2e66259f0d5bf6f", "lessThan": "00843074d9b84824552c9679d423d29500ca5de0", "status": "affected", "versionType": "git" }, { "version": "eec7620800081e27dbf8019ac2e66259f0d5bf6f", "lessThan": "f7cb90ddc021747fc9abfd4cf5252d425fd34eec", "status": "affected", "versionType": "git" }, { "version": "eec7620800081e27dbf8019ac2e66259f0d5bf6f", "lessThan": "5e4627d3513e60accfce9d5f4c7fa95251ef93d6", "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": "6.10", "status": "affected" }, { "version": "0", "lessThan": "6.10", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.109", "lessThanOrEqual": "6.12.*", "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": "6.10", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/69ed78b6b947c9257213164678b4edf17533093b" }, { "url": "https://git.kernel.org/stable/c/00843074d9b84824552c9679d423d29500ca5de0" }, { "url": "https://git.kernel.org/stable/c/f7cb90ddc021747fc9abfd4cf5252d425fd34eec" }, { "url": "https://git.kernel.org/stable/c/5e4627d3513e60accfce9d5f4c7fa95251ef93d6" } ], "title": "nfsd: drop the stateid, not the stateowner, on seqid_op replay retry", "x_generator": { "engine": "bippy-1.2.0" } } } }