CVE-2026-74401 dlm: fix add msg handle in send_queue ordered
A race condition in the Linux kernel Distributed Lock Manager can lead to use-after-free, potentially allowing local attackers to execute code or escalate privileges.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74401?
CVE-2026-74401 is a critical use after free vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
dlm: fix add msg handle in send_queue ordered
In a benchmark scenario triggering a lot of requests that triggers a lot of DLM messages on the network it can be that the mh->seq is not ordered according the oldest seq number. This ordering is required by dlm_receive_ack as "before(mh->seq, seq)" will stop to check for older sequence numbers that are ordered in the tail of "node->send_queue".
The side effects of not having it correct ordered regarding "before(mh->seq, seq)" are refcounting issues and use-after free.
I only was able to reproduce this issue in a experimental DLM branch and a user space DLM benchmark that uses io_uring. After changing this I don't experienced any refcounting with the sending buffer issues anymore.
Which versions are affected by CVE-2026-74401?
How do I fix CVE-2026-74401?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-74401 being exploited?
There is no known exploitation of CVE-2026-74401 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-74401, DEBIAN-CVE-2026-74401, GHSA-wgc9-j6gh-934m, UBUNTU-CVE-2026-74401.