270 lines
15 KiB
JSON
270 lines
15 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-89712",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2026-09-11T19:38:34.751Z",
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"datePublished": "2026-09-11T19:46:27.018Z",
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"dateUpdated": "2026-10-19T08:51:25.202Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-10-19T08:51:25.202Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"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."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 9.8,
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"baseSeverity": "CRITICAL"
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},
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"scenarios": [
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{
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"lang": "en",
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"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."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"fs/nfsd/nfs4state.c"
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],
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"versions": [
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{
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"version": "a4bc287943f5695209ff36bdc89f17b48d68fae7",
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"lessThan": "2b59029b8f24a99b5d844af2da3950d39d36eeea",
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"status": "affected",
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"status": "affected",
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"lessThan": "036c1b182f4da65363e79ec0ac276edc6b7296e5",
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"status": "affected",
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},
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{
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"version": "5.10.220",
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"lessThan": "5.10.270",
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"status": "affected",
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"versionType": "semver"
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"fs/nfsd/nfs4state.c"
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],
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{
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"status": "affected"
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},
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"version": "0",
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"lessThan": "5.14",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "5.10.270",
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"lessThanOrEqual": "5.10.*",
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"status": "unaffected",
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},
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{
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"version": "5.15.221",
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},
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"version": "6.1.188",
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"lessThanOrEqual": "6.1.*",
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"status": "unaffected",
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},
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"version": "6.6.157",
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"lessThanOrEqual": "6.6.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.12.109",
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"lessThanOrEqual": "6.12.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.18.50",
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"lessThanOrEqual": "6.18.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.2.4",
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"lessThanOrEqual": "7.2.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.3",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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}
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],
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"cpeApplicability": [
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},
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"url": "https://git.kernel.org/stable/c/659ee3da073164e1e6e40dfcbc26eeed85845f93"
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{
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"url": "https://git.kernel.org/stable/c/60680ae7243b22de3d09be990d8e23bcfc4af837"
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},
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{
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"url": "https://git.kernel.org/stable/c/77de363d9a1c8cd35f20482782c612cda085791a"
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},
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{
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"url": "https://git.kernel.org/stable/c/4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8"
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},
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{
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"url": "https://git.kernel.org/stable/c/7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9"
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},
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{
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"url": "https://git.kernel.org/stable/c/036c1b182f4da65363e79ec0ac276edc6b7296e5"
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}
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],
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"title": "NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock",
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} |