{"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":"2026-09-14T12:02:07.475Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-14T12:02:07.475Z"},"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-rc1","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-rc1"}]}]}],"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"}}}}