CVE-2026-74496 fou: Fix use-after-free in fou_create()
A use-after-free in the Linux kernel's FOU module allows attackers to potentially execute code or escalate privileges via concurrent socket operations.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74496?
CVE-2026-74496 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
fou: Fix use-after-free in fou_create()
fou_create() publishes struct fou through sk_user_data before adding the new FOU port to the per-netns list. If fou_add_to_port_list() fails, the error path frees fou while it is still reachable through sk_user_data. A concurrent receive can then dereference the freed object in fou_from_sock().
This ordering issue was previously noted in the linked discussion.
The failure is reachable when local port 0 is requested. Each socket binds to a different ephemeral port, but fou_cfg_cmp() compares the requested port 0 and reports -EALREADY once an entry already exists.
Release the tunnel socket before freeing fou so sk_user_data is cleared first, and defer reclamation with kfree_rcu() to protect concurrent RCU readers. This matches the lifetime handling in fou_release().
Which versions are affected by CVE-2026-74496?
How do I fix CVE-2026-74496?
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-2026-74496 being exploited?
There is no known exploitation of CVE-2026-74496 in the wild and no public exploit code.
Sources
Also known as AZL-96213, BELL-CVE-2026-74496, DEBIAN-CVE-2026-74496, GHSA-p6w2-3hc3-fx3j, UBUNTU-CVE-2026-74496.