namespace: don't inherit MNT_UMOUNT in clone_mnt()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98993
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-23 13:17:21 UTC
Updated2026-10-24 14:16:51 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: namespace: don't inherit MNT_UMOUNT in clone_mnt() MNT_UMOUNT gets raised on a mount that umount_tree() or umount_one() has taken out of its namespace. It's never cleared. __detach_mounts() unhooks a mount that carries it instead of unmounting it. disconnect_mount() lets an unmounted child stay attached only if its parent carries it. propagate_umount() takes it as the sign that a mount is going to be unmounted when it decides what else can be unmounted, where a chain of locked mounts ends and where a for reparenting an overmount. clone_mnt() copies the flags of the source and only masks MNT_INTERNAL_FLAGS which doesn't include MNT_UMOUNT. A mount that was lazily unmounted but is kept alive by a file descriptor can still be copied when its root is an nsfs or pidfs file because may_copy_tree() accepts those before checking whether the source is mounted at all: mount --bind /proc/self/ns/net /tmp/x exec 3< /tmp/x umount -l /tmp/x mount --bind /proc/self/fd/3 /tmp/y The mount on /tmp/y is attached to the caller's namespace with MNT_UMOUNT already set and every copy of it inherits the flag again. That causes a number of bugs: - Unlink its mountpoint from a mount namespace where it isn't one. __detach_mounts() takes it for a mount that was unmounted earlier, unhooks it from its parent and drops the reference the namespace holds on it. It stays in the namespace with one reference too few and as its own parent, so it can't be unmounted through the file descriptor anymore and the namespace never finds it again. When the namespace goes away it's leaked and points to a freed struct mnt_namespace that may_change_propagation() and anon_ns_root() read on the next propagation change or mount_setattr() through the file descriptor. - Make it shared and unmount a peer. trace_transfers() follows the flag from the peer into it and strips it from its peer group. - Let a propagated umount reach it. gather_candidates() marks it with T_UMOUNT_CANDIDATE but never puts it on the candidate list, so the mark is never cleared and every later propagated umount skips it. If it's the parent of a locked mount handle_locked() takes it as the cutoff and commits the locked child that should have stayed and disconnect_mount() leaves that child attached to it, unmounted under a mounted parent, which is what disconnect_mount() exists to prevent. When the namespace goes away umount_tree() visits the child a second time. And once __detach_mounts() has made it its own parent reparent() never finds the end of the chain of unmounted parents. A clone is a new mount that has never been unmounted. Add MNT_UMOUNT to MNT_INTERNAL_FLAGS so clone_mnt() never copies it. And warn when umount_tree() reaches a mount that already has it set.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 590ce4bcbfb4e0462a720a4ad901e84416080bba 99698cfa34e493fc091219056aae446fe9442a96 git Not specified
CNA Linux Linux affected 590ce4bcbfb4e0462a720a4ad901e84416080bba c26c1a91ad2881a194f7af543e0b57f0870006b2 git Not specified
CNA Linux Linux affected 590ce4bcbfb4e0462a720a4ad901e84416080bba eecc9cd0fc07dba3f7fb0b2f844b4029435a2f7b git Not specified
CNA Linux Linux affected 590ce4bcbfb4e0462a720a4ad901e84416080bba 5077b52e9e4d72da53c50251296b99cd416765a1 git Not specified
CNA Linux Linux affected 590ce4bcbfb4e0462a720a4ad901e84416080bba e2c6d326216642011da318b9edfd5d57ebd5a56f git Not specified
CNA Linux Linux affected 7052e71b2d085f76800115d4a212dcaf82b86262 git Not specified
CNA Linux Linux affected 4.0.2 4.1 semver Not specified
CNA Linux Linux affected 4.1 Not specified
CNA Linux Linux unaffected 4.1 semver Not specified
CNA Linux Linux unaffected 6.6.160 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.114 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.57 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.11 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/e2c6d326216642011da318b9edfd5d57ebd5a56f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/5077b52e9e4d72da53c50251296b99cd416765a1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/99698cfa34e493fc091219056aae446fe9442a96 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c26c1a91ad2881a194f7af543e0b57f0870006b2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/eecc9cd0fc07dba3f7fb0b2f844b4029435a2f7b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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