{"id":"CVE-2026-89706","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-89706","summary":"nfsd: Reset write verifier when async COPY writeback fails","details":"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.","published":"2026-09-11T19:46:22.561Z","modified":"2026-09-14T03:46:28.356761812Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.12.109"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/591134e059e3456180244a826d6917cdc183140b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bf0cd31a9abcb728c17d79b4c2cc533612a8b6af"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89706.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89706"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-14T03:46:28.356761812Z"}}