CVE-2025-71080 ipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT
A race condition in the Linux kernel IPv6 routing code under PREEMPT_RT can trigger a kernel BUG, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-71080?
CVE-2025-71080 is a high-severity vulnerability in Linux kernel, published on 13 Jan 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:
ipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT
On PREEMPT_RT kernels, after rt6_get_pcpu_route() returns NULL, the current task can be preempted. Another task running on the same CPU may then execute rt6_make_pcpu_route() and successfully install a pcpu_rt entry. When the first task resumes execution, its cmpxchg() in rt6_make_pcpu_route() will fail because rt6i_pcpu is no longer NULL, triggering the BUG_ON(prev). It's easy to reproduce it by adding mdelay() after rt6_get_pcpu_route().
Using preempt_disable/enable is not appropriate here because ip6_rt_pcpu_alloc() may sleep.
Fix this by handling the cmpxchg() failure gracefully on PREEMPT_RT: free our allocation and return the existing pcpu_rt installed by another task. The BUG_ON is replaced by WARN_ON_ONCE for non-PREEMPT_RT kernels where such races should not occur.
Weakness: CWE-617
Which versions are affected by CVE-2025-71080?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-71080?
Apply the vendor's patch.
Is CVE-2025-71080 being exploited?
There is no known exploitation of CVE-2025-71080 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-71080, DEBIAN-CVE-2025-71080, GHSA-gmq5-qgc7-64gv, ROOT-OS-DEBIAN-13-CVE-2025-71080, UBUNTU-CVE-2025-71080.