VulnerabilityPublished 23 Oct 2026Updated 24 Oct 2026

CVE-2026-98993: Linux kernel · namespace: don't inherit MNT_UMOUNT in clone_mnt()

Source GCVE Database

Authoritative record:CVE-2026-98993· High 7.8

Not known to be exploited · CVSS 7.8 High · fixed in eecc9cd0fc07dba3f7fb0b2f844b4029435a2f7b : patch Linux kernel soon.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score

7.8High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in eecc9cd0fc07dba3f7fb0b2f844b4029435a2f7b, e2c6d326216642011da318b9edfd5d57ebd5a56f, c26c1a91ad2881a194f7af543e0b57f0870006b2 +3

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

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

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-53w5-4v27-r5f4

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected >=4.0.2 <4.1	Fixed in eecc9cd0fc07dba3f7fb0b2f844b4029435a2f7b e2c6d326216642011da318b9edfd5d57ebd5a56f c26c1a91ad2881a194f7af543e0b57f0870006b2 99698cfa34e493fc091219056aae446fe9442a96 5077b52e9e4d72da53c50251296b99cd416765a1 4.1
LinuxLinux	Affected =4.1	Fixed in–

Description

In 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.

References

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