{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89712", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.751Z", "datePublished": "2026-09-11T19:46:27.018Z", "dateUpdated": "2026-10-19T08:51:25.202Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:51:25.202Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock\n\nnfsd4_ssc_expire_umount() walks nn->nfsd_ssc_mount_list with\nlist_for_each_entry_safe(ni, tmp, ...). For each expired entry it\nsets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the\nsource vfsmount, then reacquires the lock to list_del + kfree the\nentry and continue iterating via the macro's saved tmp pointer.\n\nThe nsui_busy flag protects the current ni from concurrent\nnfsd4_ssc_setup_dul() finders during the lock-drop window, but it\ndoes not pin tmp. Another nfsd RPC thread that fails its source-\nserver mount and reaches nfsd4_ssc_cancel_dul() will, during that\nsame window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount\nitem, and release the lock. If that item is the saved tmp of the\nexpire walk, the next iteration dereferences a freed\nnfsd4_ssc_umount_item.\n\nRestart the walk from the head after the mntput() unlock window so\nno saved next pointer survives the lock-drop. The list is bounded\nby the number of active inter-server source mounts (typically small)\nand the expire delayed-work runs periodically rather than per-IO,\nso the restart is cheap." } ], "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 - The UAF is between nfsd4_ssc_expire_umount() and nfsd4_ssc_cancel_dul(); cancel_dul runs from nfsd4_copy() on NFSv4.2 OP_COPY, reached by a COMPOUND over TCP/2049 to in-kernel nfsd. A remote client populates nfsd_ssc_mount_list and frees the saved iterator with no local access.\nAC:L - The attacker drives both race sides with concurrent async inter-server COPY requests: completed copies leave expired nfsd4_ssc_umount_item entries for the laundromat, while a COPY to another source IP fails vfs_kern_mount() into cancel_dul() during mntput(). An attacker-controlled source NFS server can stall unmount, so the window is attacker-created and retryable.\nPR:N - Under AUTH_SYS (default for typical NFS deployments) the server verifies no secret; EXCHANGE_ID, CREATE_SESSION, and OPEN succeed for any host allowed by the export, so no server-verified privileges are required to issue the COPY compounds that hit setup_dul/cancel_dul.\nUI:N - The attacker’s own NFS client issues the COPY compounds and source-server traffic that create, expire, and cancel ssc_umount items; no administrator or other user action on the victim server is required.\nS:U - The use-after-free is of a kmalloc’d nfsd4_ssc_umount_item in the nfsd host kernel; impact stays within the same kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - After cancel_dul() kfree()s the saved tmp, the expire walk continues from a freed nfsd4_ssc_umount_item whose vfsmount, list links, and metadata the attacker can replace via slab reuse, giving a UAF read primitive over kernel heap.\nI:H - The expire path then writes nsui_busy, calls mntput() on attacker-controlled nsui_vfsmount, and runs list_del()/kfree() on poisoned pointers, yielding arbitrary-write and control-flow hijack primitives from the same UAF.\nA:H - Dereferencing the freed list node in nfsd4_ssc_expire_umount() oopses or panics the laundromat worker even without a full exploit, taking down the in-kernel NFS server." } ] } ], "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": "a4bc287943f5695209ff36bdc89f17b48d68fae7", "lessThan": "2b59029b8f24a99b5d844af2da3950d39d36eeea", "status": "affected", "versionType": "git" }, { "version": "f4e44b393389c77958f7c58bf4415032b4cda15b", "lessThan": "d9e151fea5ed706c1284adacabd869b0be745db2", "status": "affected", "versionType": "git" }, { "version": "f4e44b393389c77958f7c58bf4415032b4cda15b", "lessThan": "659ee3da073164e1e6e40dfcbc26eeed85845f93", "status": "affected", "versionType": "git" }, { "version": "f4e44b393389c77958f7c58bf4415032b4cda15b", "lessThan": "60680ae7243b22de3d09be990d8e23bcfc4af837", "status": "affected", "versionType": "git" }, { "version": "f4e44b393389c77958f7c58bf4415032b4cda15b", "lessThan": "77de363d9a1c8cd35f20482782c612cda085791a", "status": "affected", "versionType": "git" }, { "version": "f4e44b393389c77958f7c58bf4415032b4cda15b", "lessThan": "4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8", "status": "affected", "versionType": "git" }, { "version": "f4e44b393389c77958f7c58bf4415032b4cda15b", "lessThan": "7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9", "status": "affected", "versionType": "git" }, { "version": "f4e44b393389c77958f7c58bf4415032b4cda15b", "lessThan": "036c1b182f4da65363e79ec0ac276edc6b7296e5", "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/nfs4state.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/2b59029b8f24a99b5d844af2da3950d39d36eeea" }, { "url": "https://git.kernel.org/stable/c/d9e151fea5ed706c1284adacabd869b0be745db2" }, { "url": "https://git.kernel.org/stable/c/659ee3da073164e1e6e40dfcbc26eeed85845f93" }, { "url": "https://git.kernel.org/stable/c/60680ae7243b22de3d09be990d8e23bcfc4af837" }, { "url": "https://git.kernel.org/stable/c/77de363d9a1c8cd35f20482782c612cda085791a" }, { "url": "https://git.kernel.org/stable/c/4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8" }, { "url": "https://git.kernel.org/stable/c/7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9" }, { "url": "https://git.kernel.org/stable/c/036c1b182f4da65363e79ec0ac276edc6b7296e5" } ], "title": "NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock", "x_generator": { "engine": "bippy-1.2.0" } } } }