CVE-2026-98991: Linux kernel · namespace: queue a mount only once for mount notifications
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High.
Data as of 28 Oct 2026, 01:58 UTC
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation 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
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.10linuxpkg:deb/ubuntu/linux?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix is available that initializes the notification list properly and ensures mounts are queued only once for mount notifications. Users should apply the updated Linux kernel versions that include this patch. No additional mitigation steps are indicated or necessary beyond applying the official fix.
Description
CVE-2026-98991 is a high-severity vulnerability in the Linux kernel related to mount notification handling. The flaw arises because the kernel function mnt_notify_add() can queue a mount multiple times without checking if it is already queued, leading to use-after-free memory access. This occurs during complex mount namespace operations involving multiple unmounts under a single namespace semaphore hold. The issue can cause kernel memory corruption and crashes due to accessing freed memory. The vulnerability affects specific Linux kernel versions listed and has a CVSS score of 7.8. A fix involves initializing the notification list properly and ensuring mounts are queued only once.
References
- ubuntu.com/security/CVE-2026-98991 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-98991 (opens in a new tab)
- git.kernel.org/stable/c/702ff3fe499876e09c45558a05366d21a5bc41ab (opens in a new tab)
- git.kernel.org/stable/c/acbe9e4418e2ef7bef1a12e62e0e7d6145a15190 (opens in a new tab)
- git.kernel.org/stable/c/bd2feb7796b6585938a4241e7b7c4148a6f7b762 (opens in a new tab)