CVE-2026-98977: Linux kernel · namespace: handle mount locking for automounts correctly
Source GCVE Database
Not known to be exploited · fixed in e01c79761c7b3373e80094c5eadb21cb864fa8bc : update Linux kernel when convenient.
Data as of 26 Oct 2026, 17:16 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in e01c79761c7b3373e80094c5eadb21cb864fa8bc, b3ccde78f1608836e62320428abc0e8aa9cf2329, 33aadc7c72055fca93cb5a3691d836ebf8b31c9b +3
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.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in– |
Description
In the Linux kernel, the following vulnerability has been resolved: namespace: handle mount locking for automounts correctly If mounts are propagated across user namespaces, attach_recursive_mnt() locks every copy of the source mount to protect overmounts from vanishing and revealing the underlying files or directories. The user namespace is taken from the caller's mount namespaces since this is where the mounts end up. Except, that's not always true. Automounts may legitimately get popped in by tasks located in a different mount and user namespace during path lookup. Then check doesn't make sense at that point. The copy in the namespace of the parent - which may be the host's - is now locked and the host cannot change the flags of its own mounts anymore. Here's the reproducer: - host has debugfs mounted nosuid,nodev,noexec and shared - tracefs automount below it is not yet active - hand a child process a directory descriptor on that mount - child process enters auser and mount namespace - child process' namespace now holds a locked copy of the host's debugfs mount that receives propagation from it - child process stats "tracing/." through the descriptor - lookup runs on the host's mount so the automount lands below the host's mount - propagation puts a copy below the child's copy - both try to clear the flags on the mount they got, with a bind remount: host, on its own automount: MS_REMOUNT|MS_BIND = EPERM child, on the copy in its namespace: MS_REMOUNT|MS_BIND = 0 So the lock landed on the host's mount instead of the child's copy. Congrats. So we need to compare with the owner of the namespace the mount actually gets mounted on. For all regular cases that is the caller's mount namespace and so nothing changes. Detached trees in anonymous mount namespaces by be handed over via SCM_RIGHTS or inherited in other ways on purpose so the attaching task's mount namespace is authoritative, not the creator of the detached tree.
References
- nvd.nist.gov/vuln/detail/CVE-2026-98977 (opens in a new tab)
- git.kernel.org/stable/c/33aadc7c72055fca93cb5a3691d836ebf8b31c9b (opens in a new tab)
- git.kernel.org/stable/c/5e8f3ac8fa3d411b422ad32b9168c46a4824cc79 (opens in a new tab)
- git.kernel.org/stable/c/6ab37fae14196ba2262b152a7d9222c50356d278 (opens in a new tab)
- git.kernel.org/stable/c/b3ccde78f1608836e62320428abc0e8aa9cf2329 (opens in a new tab)
- git.kernel.org/stable/c/e01c79761c7b3373e80094c5eadb21cb864fa8bc (opens in a new tab)