VulnerabilityPublished 28 Oct 2026

CVE-2026-99172: Linux kernel · ipc: drop the mqueue mount with kern_unmount() on setup failure

Affects Linux kernelSource CVE Database V5

Not known to be exploited : upgrade to f0e48172a59e517e613b73f73cc35f24fd123aeb or c0620b648321fff654173d238d4a85298ea16d05 when convenient.

Data as of 28 Oct 2026, 10:58 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

Patch: Available – fixed in f0e48172a59e517e613b73f73cc35f24fd123aeb, c0620b648321fff654173d238d4a85298ea16d05

Exploitation evidence

Disclosed: evidence found.
CVE published 28 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.

What to do

Upgrade Linux kernel to f0e48172a59e517e613b73f73cc35f24fd123aeb or c0620b648321fff654173d238d4a85298ea16d05.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ dc55e35f9e810f23dd69cfdc91a3d636023f57a2, < f0e48172a59e517e613b73f73cc35f24fd123aeb	Fixed in f0e48172a59e517e613b73f73cc35f24fd123aeb
LinuxLinux	Affected ≥ dc55e35f9e810f23dd69cfdc91a3d636023f57a2, < c0620b648321fff654173d238d4a85298ea16d05	Fixed in c0620b648321fff654173d238d4a85298ea16d05
LinuxLinux	Affected =5.19	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: ipc: drop the mqueue mount with kern_unmount() on setup failure mq_init_ns() creates the mqueue mount with fc_mount_longterm(), so its ->mnt_ns is MNT_NS_INTERNAL. When setting up the mqueue or ipc sysctls or msg_init_ns() fails afterwards, create_ipc_ns() drops it with a plain mntput(). With ->mnt_ns set that takes the fast path of mntput_no_expire(). The count drops to zero and nothing ever kills the mount, so the mount and the mqueue superblock are leaked. Commit dc55e35f9e81 ("ipc: Store mqueue sysctls in the ipc namespace") added the first failure path after mq_init_ns() and never dropped the mount. Commit 7229d74e5e8c ("ipc: create_ipc_ns: drop mqueue mount on sysctl setup failure") tried to fix that with a mntput() but that doesn't help for a long-term mount. Use kern_unmount(). free_ipc() open-codes the same thing for a namespace that made it.

References

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