{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-98991", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.384Z", "datePublished": "2026-10-23T12:20:10.289Z", "dateUpdated": "2026-10-24T14:09:52.901Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-24T14:09:52.901Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: queue a mount only once for mount notifications\n\nmnt_notify_add() puts a mount on notify_list. It doesn't check whether\nthe mount is on the list already. That's fine as long as every mount is\nqueued at most once per namespace_sem hold. It isn't.\n\npropagate_umount() moves a surviving overmount off a stack of mounts\nthat are going away and queues it as moved. shrink_submounts() and\nmark_mounts_for_expiry() call umount_tree() for several mounts under a\nsingle namespace_sem hold. So the second umount_tree() can take down\nexactly the mount the first one reparented, reparent it once more and so\nend up queueing it a second time.\n\nThe second list_add_tail() cuts the mounts queued in between out of the\nlist while the head still points at the last of them. notify_mnt_list()\nthen only visits that one mount and the others are freed after the grace\nperiod with notify_list still pointing at them. Every later mount\noperation on the host walks freed memory:\n\n BUG: KASAN: slab-use-after-free in __list_add_valid_or_report\n Read of size 8 at addr ffff8881003d57e0 by task notify_dq/162\n __list_add_valid_or_report+0x15c/0x1a0\n mnt_add_to_ns+0x322/0x890\n attach_recursive_mnt.isra.0+0xf2a/0x1a00\n path_mount+0x139c/0x1d40\n\nThis needs a mount with MNT_SHRINKABLE to bind from. That's what\nfinish_automount() creates (submounts of NFS, AFS and CIFS and the\ntracefs mount below debugfs). Bind mounts inherit the flag. A mount\nnamespace with a FAN_MARK_MNTNS mark does the rest and root in a user\nnamespace can have both.\n\nInitialize to_notify in alloc_vfsmnt() and leave a mount alone that is\nqueued already. mnt_notify() looks at the state the mount has when the\nlist is drained so a single entry per mount is enough. The move event\nfor a mount that is unmounted under the same hold is lost. That's fine.\nThe detach is what matters." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Local umount(2) follows ksys_umount()->path_umount()->do_umount()->shrink_submounts()->umount_tree()->propagate_umount()->reparent()->mnt_notify_add(), the function patched; no network protocol supplies the triggering mount topology.\nAC:L - With a reachable MNT_SHRINKABLE automount, the attacker can create the required bind, shared/slave, and overmount topology and synchronously unmount it; duplicate queueing occurs sequentially under one namespace_sem hold and requires no race.\nPR:L - may_mount() and FAN_MARK_MNTNS use CAP_SYS_ADMIN relative to the attacker-owned mount/group/target user namespaces; unshare(CLONE_NEWUSER|CLONE_NEWNS) gives an ordinary local user those namespace-scoped capabilities without init-namespace privilege.\nUI:N - The attacker personally creates the fanotify mark and mount topology and invokes umount(2); no victim must mount media, open a file, or perform another action.\nS:U - The corrupted global notify_list and freed struct mount objects are resources of the same host kernel reached by the attacker; this is a kernel privilege-escalation boundary, not a guest-host, IOMMU, or other scope change.\nC:H - notify_mnt_list() leaves notify_list linked through freed struct mount::to_notify nodes, so later mount operations dereference attacker-reclaimable mnt_cache objects; this kernel-heap UAF can be leveraged to disclose kernel memory.\nI:H - After the stale to_notify node is freed or reallocated, __list_add() in mnt_notify_add() writes next->prev and prev->next through the corrupted list links, providing exploitable kernel-heap corruption capable of control-flow hijacking.\nA:H - namespace_unlock() frees mounts still referenced by notify_list, and a later path_mount()->mnt_add_to_ns()->mnt_notify_add() provably reads the freed node, producing the documented KASAN slab-use-after-free and a host kernel oops or panic." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/mount.h", "fs/namespace.c" ], "versions": [ { "version": "bf630c40164162ba1d3933c2f5e3397d083e0948", "lessThan": "acbe9e4418e2ef7bef1a12e62e0e7d6145a15190", "status": "affected", "versionType": "git" }, { "version": "bf630c40164162ba1d3933c2f5e3397d083e0948", "lessThan": "702ff3fe499876e09c45558a05366d21a5bc41ab", "status": "affected", "versionType": "git" }, { "version": "bf630c40164162ba1d3933c2f5e3397d083e0948", "lessThan": "bd2feb7796b6585938a4241e7b7c4148a6f7b762", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/mount.h", "fs/namespace.c" ], "versions": [ { "version": "6.15", "status": "affected" }, { "version": "0", "lessThan": "6.15", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.57", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.11", "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": "6.15", "versionEndExcluding": "6.18.57" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "7.2.11" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/acbe9e4418e2ef7bef1a12e62e0e7d6145a15190" }, { "url": "https://git.kernel.org/stable/c/702ff3fe499876e09c45558a05366d21a5bc41ab" }, { "url": "https://git.kernel.org/stable/c/bd2feb7796b6585938a4241e7b7c4148a6f7b762" } ], "title": "namespace: queue a mount only once for mount notifications", "x_generator": { "engine": "bippy-1.2.0" } } } }