VulnerabilityPublished 23 Oct 2026

CVE-2026-98987: Linux kernel · namespace: look at the topmost mount for a mount namespace file

Source GCVE Database

Authoritative record:CVE-2026-98987· Medium

Not known to be exploited · fixed in b9c40553f6ceba50042281eef6f701e5fb719726 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 13:47 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in b9c40553f6ceba50042281eef6f701e5fb719726, 8714b44adac7b10506e1db3ef1710689751f0f10, 87ecd4c6da146363384a603bd9e90c90e7275536

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-8fp8-xwh3-vf8f

What to do

Upgrade Linux kernel to b9c40553f6ceba50042281eef6f701e5fb719726, 8714b44adac7b10506e1db3ef1710689751f0f10 or 87ecd4c6da146363384a603bd9e90c90e7275536.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 96f5d2e051653f2cfe9137c5d3c7794c358ffb03, < b9c40553f6ceba50042281eef6f701e5fb719726	Fixed in b9c40553f6ceba50042281eef6f701e5fb719726
LinuxLinux	Affected ≥ 96f5d2e051653f2cfe9137c5d3c7794c358ffb03, < 8714b44adac7b10506e1db3ef1710689751f0f10	Fixed in 8714b44adac7b10506e1db3ef1710689751f0f10
LinuxLinux	Affected ≥ 96f5d2e051653f2cfe9137c5d3c7794c358ffb03, < 87ecd4c6da146363384a603bd9e90c90e7275536	Fixed in 87ecd4c6da146363384a603bd9e90c90e7275536
LinuxLinux	Affected =6.17	Fixed in–

AI-suggested

The vulnerability has been resolved in the Linux kernel. No specific patch links are provided in the input data. Users should apply the official Linux kernel updates that address this issue once available.

Description

A vulnerability in the Linux kernel's mount namespace handling has been resolved. The flaw involves attach_recursive_mnt() not properly considering the topmost mount in a mount namespace file chain, leading to incorrect mountpoint attachment. This can cause mounts to become inaccessible and prevent synchronous unmounting due to lingering child mounts.

Impact

Affected systems may experience mounts becoming inaccessible and inability to synchronously unmount certain mounts, potentially causing resource management issues and operational disruptions related to mount namespace handling. There is no indication of remote code execution or privilege escalation from the provided data.

Summary

The vulnerability in the Linux kernel relates to the attach_recursive_mnt() function, which preallocates a mountpoint for the root of the topmost mount of the source. The issue arises because the loop that walks up the mount chain does not consider the topmost mount itself. If the topmost mount is the only mount namespace file in the chain, the variable 'shorter' remains NULL, causing mnt_change_mountpoint() to attach the existing mount below the root of the mount namespace file (a nsfs dentry). This results in the mount being effectively hidden until its parent is removed, and the copy that replaced it cannot be unmounted synchronously due to having a child mount. The problem manifests in scenarios involving bind mounts and shared/slave mount relationships, leading to unexpected content visibility and EBUSY errors on unmount attempts.

References

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