# CVE-2026-98991: linux: In the Linux kernel, the following vulnerability has been resolved:  namespace: queue a mount only once for mount not...

CVE-2026-98991 is fixed in linux on 1 platform by DEBIAN-CVE-2026-98991 (version 7.2.11-1), released October 24, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-98991
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0016
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 23, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  namespace: queue a mount only once for mount notifications  mnt_notify_add() puts a mount on notify_list. It doesn't check whether the mount is on the list already. That's fine as long as every mount is queued at most once per namespace_sem hold. It isn't.  propagate_umount() moves a surviving overmount off a stack of mounts that are going away and queues it as moved. shrink_submounts() and mark_mounts_for_expiry() call umount_tree() for several mounts under a single namespace_sem hold. So the second umount_tree() can take down exactly the mount the first one reparented, reparent it once more and so end up queueing it a second time.  The second list_add_tail() cuts the mounts queued in between out of the list while the head still points at the last of them. notify_mnt_list() then only visits that one mount and the others are freed after the grace period with notify_list still pointing at them. Every later mount operation on the host walks freed memory:    BUG: KASAN: slab-use-after-free in __list_add_valid_or_report   Read of size 8 at addr ffff8881003d57e0 by task notify_dq/162    __list_add_valid_or_report+0x15c/0x1a0    mnt_add_to_ns+0x322/0x890    attach_recursive_mnt.isra.0+0xf2a/0x1a00    path_mount+0x139c/0x1d40  This needs a mount with MNT_SHRINKABLE to bind from. That's what finish_automount() creates (submounts of NFS, AFS and CIFS and the tracefs mount below debugfs). Bind mounts inherit the flag. A mount namespace with a FAN_MARK_MNTNS mark does the rest and root in a user namespace can have both.  Initialize to_notify in alloc_vfsmnt() and leave a mount alone that is queued already. mnt_notify() looks at the state the mount has when the list is drained so a single entry per mount is enough. The move event for a mount that is unmounted under the same hold is lost. That's fine. The detach is what matters.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.2.11-1 | [DEBIAN-CVE-2026-98991](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98991.md) | Oct 24, 2026 |

---

Data as of 2026-11-09T13:31:49Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.