VulnerabilityPublished 23 Oct 2026

CVE-2026-98992: Linux kernel · namespace: don't copy an unmounted mount tree

Source GCVE Database

Authoritative record:CVE-2026-98992· Medium

Not known to be exploited · fixed in b47b40c4f058418f9707454543179df240796aad : update Linux kernel when convenient.

Data as of 26 Oct 2026, 14:05 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

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 b47b40c4f058418f9707454543179df240796aad, 86a2d56b1960720bf1844441c0890621e9db2f25, 8d3527457e183cedee3003c2897314da49488311 +2

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-p9pg-23xc-8cjw

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ e149ed2b805fefdccf7ccdfc19eca22fdd4514ac, < b47b40c4f058418f9707454543179df240796aad	Fixed in b47b40c4f058418f9707454543179df240796aad
LinuxLinux	Affected ≥ e149ed2b805fefdccf7ccdfc19eca22fdd4514ac, < 86a2d56b1960720bf1844441c0890621e9db2f25	Fixed in 86a2d56b1960720bf1844441c0890621e9db2f25
LinuxLinux	Affected ≥ e149ed2b805fefdccf7ccdfc19eca22fdd4514ac, < 8d3527457e183cedee3003c2897314da49488311	Fixed in 8d3527457e183cedee3003c2897314da49488311
LinuxLinux	Affected ≥ e149ed2b805fefdccf7ccdfc19eca22fdd4514ac, < 8bacbf6be959973b28b691713a872c12eae69eec	Fixed in 8bacbf6be959973b28b691713a872c12eae69eec
LinuxLinux	Affected ≥ e149ed2b805fefdccf7ccdfc19eca22fdd4514ac, < 7e037b1fd339d865737c8accd29abcf40130a5a0	Fixed in 7e037b1fd339d865737c8accd29abcf40130a5a0
LinuxLinux	Affected =3.19	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: namespace: don't copy an unmounted mount tree may_copy_tree() accepts a mount whose root is an nsfs or pidfs file before it checks whether that mount is mounted. This exception exists for nsfs and pidfs mounts. They are part of no mount namespace so neither check_mnt() nor is_mounted() would let them through and bind-mounting a nsfsfd or a pidfd wouldn't work. Problem is that exception also admits a bind mount of such a file when it was lazily unmounted and is only kept alive by a file descriptor: mount --bind /proc/self/ns/net /tmp/x exec 3< /tmp/x umount -l /tmp/x mount --rbind /proc/self/fd/3 /tmp/y With MS_REC or AT_RECURSIVE copy_tree() doesn't stop at the unmounted mount. It copies every mount that stayed attached to it as well. So if you have a bunch of overmounts over the nsfsfd or the pidfd the whole unmounted stack is copied. That's a bug. So refuse to walk an unmounted tree. Copying its root alone stays possible. So a bind mount of a namespace that is gone can still be recreated from a file descriptor on the old one. The file descriptor pins that mount and its root and __has_locked_children() only reads the direct children which don't leave the parent's list without namespace_sem. The internal mounts carry MNT_NS_INTERNAL instead of NULL and are still walked. Copying an unmounted tree recursively fails with EINVAL.

References

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