{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89706", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.751Z", "datePublished": "2026-09-11T19:46:22.561Z", "dateUpdated": "2026-10-19T08:51:19.292Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:51:19.292Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: Reset write verifier when async COPY writeback fails\n\nAsync COPY captures nn->writeverf at request time and reports it to\nthe client via CB_OFFLOAD after the worker kthread completes. When\nthe post-copy vfs_fsync_range() or filemap_check_wb_err() in\n_nfsd_copy_file_range() reports an error, the worker correctly\nleaves NFSD4_COPY_F_COMMITTED clear so that CB_OFFLOAD encodes\nwr_stable_how as NFS_UNSTABLE, but the server's write verifier is\nnot rotated.\n\nA client that receives NFS_UNSTABLE in CB_OFFLOAD follows up with\nCOMMIT to make the copied data durable. With the verifier\nunchanged, COMMIT returns the same value the client just received\nvia CB_OFFLOAD, and the client concludes the copy is durable --\nsilently dropping the data whose writeback in fact failed. This\nviolates the UNSTABLE+COMMIT durability contract (RFC 7862 section\n15.1, RFC 8881 section 18.32) and matches the bug just fixed in\nnfsd_vfs_write() and nfsd_commit().\n\nRotate nn->writeverf at the writeback-failure site. The async COPY\nworker has no svc_rqst, so commit_reset_write_verifier() is not\navailable here; calling nfsd_reset_write_verifier() directly\nmirrors the trace-less reset already used by\nnfsd_file_check_write_error() for the same purpose. Filter out\n-EAGAIN and -ESTALE, matching commit_reset_write_verifier(), since\nneither indicates a durable-storage failure." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - The bug is in nfsd's NFSv4.2 async COPY worker (_nfsd_copy_file_range), reached by sending a COMPOUND with OP_COPY (ca_synchronous=false) to the in-kernel NFS server over TCP/2049. No local access to the server is required.\nAC:L - A client can induce the writeback-failure path by filling the export or hitting quota so vfs_fsync_range()/filemap_check_wb_err() returns ENOSPC/EDQUOT after the copy dirties pages, then issue async COPY; CB_OFFLOAD UNSTABLE plus COMMIT with an unchanged verifier is the specified client sequence and needs no race.\nPR:N - Default nfsd deployments use AUTH_SYS/AUTH_NULL with IP-based exports and no cryptographic authentication, so any host allowed by the export can EXCHANGE_ID/CREATE_SESSION, OPEN source and destination files, and issue async COPY by asserting a uid.\nUI:N - The attacking NFS client issues COPY, receives CB_OFFLOAD, and sends COMMIT itself. No administrator or end-user action on the NFS server is required beyond nfsd already serving an NFSv4.2 export.\nS:U - Silent durability failure affects file data on the exported filesystem in the same kernel security authority as nfsd. This is not a VM escape, IOMMU bypass, or sandbox breakout.\nC:N - The defect only skips rotating nn->writeverf after a failed COPY fsync; it does not read out-of-bounds, leak kernel memory, or disclose file contents beyond ordinary NFS access.\nI:H - vfs_fsync_range() consumes the writeback error, COMMIT then returns the same verifier, and the client drops the UNSTABLE copy as durable, silently discarding destination file data. Entire COPY ranges, including whole-file copies, can be lost while applications treat them as persisted.\nA:N - The missing verifier rotation does not oops, panic, deadlock, or hang nfsd; the server continues serving RPCs. Impact is incorrect durability reporting and data loss, not loss of the NFS service itself." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/nfs4proc.c" ], "versions": [ { "version": "817c6eb975798647c4bbbfc9eb288aa413ec7f65", "lessThan": "cc5f7cef0659a27c13dd33edd8e2f79257b095c6", "status": "affected", "versionType": "git" }, { "version": "eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d", "lessThan": "c6d2f6372c7e0f76b9c148ff7696aec64da0b5b7", "status": "affected", "versionType": "git" }, { "version": "eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d", "lessThan": "8a08ffe73eb2aa6bc6f88763da7e2b55bab6493a", "status": "affected", "versionType": "git" }, { "version": "eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d", "lessThan": "6b13d26cc21b6320a3c61d5e4cee2ce9a589b181", "status": "affected", "versionType": "git" }, { "version": "eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d", "lessThan": "31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0", "status": "affected", "versionType": "git" }, { "version": "eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d", "lessThan": "591134e059e3456180244a826d6917cdc183140b", "status": "affected", "versionType": "git" }, { "version": "eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d", "lessThan": "bf0cd31a9abcb728c17d79b4c2cc533612a8b6af", "status": "affected", "versionType": "git" }, { "version": "eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d", "lessThan": "f5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9", "status": "affected", "versionType": "git" }, { "version": "5.10.220", "lessThan": "5.10.270", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/nfs4proc.c" ], "versions": [ { "version": "5.14", "status": "affected" }, { "version": "0", "lessThan": "5.14", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.270", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.221", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.188", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.157", "lessThanOrEqual": "6.6.*", "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": "5.10.220", "versionEndExcluding": "5.10.270" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "5.15.221" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "6.1.188" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/cc5f7cef0659a27c13dd33edd8e2f79257b095c6" }, { "url": "https://git.kernel.org/stable/c/c6d2f6372c7e0f76b9c148ff7696aec64da0b5b7" }, { "url": "https://git.kernel.org/stable/c/8a08ffe73eb2aa6bc6f88763da7e2b55bab6493a" }, { "url": "https://git.kernel.org/stable/c/6b13d26cc21b6320a3c61d5e4cee2ce9a589b181" }, { "url": "https://git.kernel.org/stable/c/31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0" }, { "url": "https://git.kernel.org/stable/c/591134e059e3456180244a826d6917cdc183140b" }, { "url": "https://git.kernel.org/stable/c/bf0cd31a9abcb728c17d79b4c2cc533612a8b6af" }, { "url": "https://git.kernel.org/stable/c/f5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9" } ], "title": "nfsd: Reset write verifier when async COPY writeback fails", "x_generator": { "engine": "bippy-1.2.0" } } } }