CVE-2026-97940 ipv6: fix fib6 walker UAF on seq stop
A use-after-free in the Linux kernel IPv6 route walker allows attackers to execute arbitrary code or escalate privileges via crafted network 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-2026-97940?
CVE-2026-97940 is a high-severity use after free vulnerability in Linux, published on 25 Sep 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:
ipv6: fix fib6 walker UAF on seq stop
ipv6_route_iter_active() treats a walker in FWS_U at the table root as already unlinked. fib6_del_route() can move a still-linked walker into that same state when the current leaf is the last route at the root, so ipv6_route_native_seq_stop() skips fib6_walker_unlink(). The seq private object can then be freed while it remains on net->ipv6.fib6_walkers. A later route deletion walks the dangling list and uses the freed walker.
Use the list head as membership state and reinitialize it when unlinking. Keep the existing w->node check so a never-started iterator with a zeroed private object is not treated as linked.
The same stop helper is used by /proc/net/ipv6_route and by the BPF ipv6_route iterator. The BPF show path only widens the race.
Which versions are affected by CVE-2026-97940?
How do I fix CVE-2026-97940?
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-2026-97940 being exploited?
There is no known exploitation of CVE-2026-97940 in the wild and no public exploit code.
Sources
Also known as AZL-104700, BELL-CVE-2026-97940, DEBIAN-CVE-2026-97940, GHSA-g66h-hcwj-f29f, UBUNTU-CVE-2026-97940.