CVE-2026-98991: In the Linux kernel, the following vulnerability has been resolved: namespace: queue a mount only once for mount notifications mnt_notify

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 o

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

Description from the National Vulnerability Database, published by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

What it means for a small business

Linux is on the computers, phones or browsers your team uses every day. Turn on automatic updates and restart: most of these fixes only take effect after a restart.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.16%, higher than 4% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 28, 2026, updated daily.

Check your own setup

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Server check: what your web server says about itself, and whether that version has known flaws.

Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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