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CVE-2026-98978— namespace: never expire a locked mount

Quick assessment

Affected

Linux Linux

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复：命名空间：永远不会过期一个被锁定的挂载点。被锁定的挂载点具有特殊性，它们能够保护其下方的文件和目录不被泄露。函数会拒绝卸载被锁定的挂载点，但函数却没有这一限制。一个可收缩的挂载点，当某个用户命名空间的所有者通过操作将其移动到一个被锁定的挂载点之下时，该挂载点就会变为被锁定状态。此时，锁定属性会转移到底部的挂载点上，从而导致顶部的挂载点可以被卸载。因此，对一个未锁定的祖先挂载点执行操作时，会先过期（卸载）底部的挂载点，从而暴露出被覆盖的目录：修复方案是：让

CVSS 8.4 · High EPSS 0.21% · P10 Updated Oct 24, 2026

Possible ATT&CK Techniques 2 AI

T1083 · File and Directory Discovery T1069 · Permission Groups Discovery

Affected Version Matrix 8

Vendor	Product	Version Range	Status
Linux	Linux	`5ff9d8a65ce80efb509ce4e8051394e9ed2cd942< 6b8dc3713a76346d212abab46cbfc8d7070f534c`	affected
		`5ff9d8a65ce80efb509ce4e8051394e9ed2cd942< d23265a12e4991ce7aedce670c0b6b598cadb644`	affected
		`5ff9d8a65ce80efb509ce4e8051394e9ed2cd942< f78ddcc872248c7aa1d7e904928441a0be4c6d5d`	affected
		`3.12`	affected
		`< 3.12`	unaffected
		`6.18.57≤ 6.18.*`	unaffected
		`7.2.11≤ 7.2.*`	unaffected
		`7.3≤ *`	unaffected

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Vulnerability Information

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Vulnerability Title

namespace: never expire a locked mount

Source: CVE Program / CVE List V5

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: namespace: never expire a locked mount Locked mounts are special. They protect the underlying files and directories from being revealed. do_umount() refuses to unmount locked mounts but shrink_submounts() doesn't. A shrinkable mount can become locked once the owner of a user namespace puts it beneath a locked mount with MOVE_MOUNT_BENEATH. The locked property now moves to the mount at the bottom making it possible to unmount the top mount. So umount() of an unlocked ancestor now expires the bottom mount first and the covered directory is revealed: move_mount(c -> x/hidden, MOVE_MOUNT_BENEATH) = 0 the cover after the lock moved: umount2(x/hidden) = 0 the holder of the lock: umount2(x/hidden) = EINVAL the root of the copy, busy: umount2(x) = EBUSY reads x/hidden/secret: "covered-by-root" So leave a locked mount alone as it dies together with its parent. A plain umount() of an unlocked mount with a locked one below it is EBUSY from now on. It's the same for any other locked child. A lazy umount still takes the whole tree. mark_mounts_for_expiry() never sees a locked mount. lock_mnt_tree() leaves a mount on an expiry list alone and nothing else puts a locked one on such a list. Add an assert for this.

Source: CVE Program / CVE List V5

CVSS Information

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

Source: CVE Program / CVE List V5

Vulnerability Type

N/A

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
Linux	Linux	5ff9d8a65ce80efb509ce4e8051394e9ed2cd942 ~ 6b8dc3713a76346d212abab46cbfc8d7070f534c	-
Linux	Linux	3.12	-

II. Public POCs for CVE-2026-98978

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-98978

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Patches & Fixes for CVE-2026-98978 (1)

🔗 namespace: never expire a locked mount - kernel/git/stable/linux.git - Linux kernel stable tree

https://www.cve.org/CVERecord?id=CVE-2026-98978

Same Patch Batch · Linux · 2026-10-23 · 218 CVEs total

CVE-2026-98959	9.8 CRITICAL	btrfs: fix xattr replace when multiple xattrs are packed in the same item
CVE-2026-99079	9.8 CRITICAL	net/mlx5e: Prevent stale XSK buffer release on refill retry
CVE-2026-99078	9.8 CRITICAL	net/mlx5e: Prevent stale XSK buffer release on MPWQE refill retry
CVE-2026-98870	8.8 HIGH	ksmbd: remove stale channels from all sessions on teardown
CVE-2026-98988	8.8 HIGH	namespace: keep covered mounts covered in OPEN_TREE_NAMESPACE
CVE-2026-99083	8.8 HIGH	ksmbd: fix heap out-of-bounds write in krb5_authenticate()
CVE-2026-99082	8.8 HIGH	KVM: x86: Use active memslots for the per-vCPU MMIO cache
CVE-2026-98981	8.8 HIGH	namespace: unhash a dentry before detaching the mounts on it
CVE-2026-98980	8.8 HIGH	namei: don't reveal overmounted entries in refwalk
CVE-2026-99042	8.4 HIGH	io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6
CVE-2026-99064	8.1 HIGH	cipso: adjust cached option offsets when removing CIPSO
CVE-2026-98968	8.1 HIGH	amt: send the relay's General Query directly from the receive path
CVE-2026-98889	7.8 HIGH	wifi: iwlwifi: mvm: fix sched scan IE sizing
CVE-2026-98991	7.8 HIGH	namespace: queue a mount only once for mount notifications
CVE-2026-98976	7.8 HIGH	namespace: keep the lock on a mount that a propagated copy is moved beneath
CVE-2026-98944	7.8 HIGH	HID: steam: Refactor registration
CVE-2026-99056	7.8 HIGH	strparser: make sure __strp_recv isn't running before tearing down the parser
CVE-2026-98999	7.8 HIGH	drm/xe: Fix stale pinned_link entry when fb-pin performs the final unpin
CVE-2026-99054	7.8 HIGH	tipc: destroy topsrv workqueues before closing connections
CVE-2026-99032	7.8 HIGH	net/smc: protect clcsock lifetime in smc_getname

Showing top 20 of 218 CVEs. View all on vendor page → →

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