CVE-2025-38067 rseq: Fix segfault on registration when rseq_cs is non-zero
A local attacker can cause a kernel segfault by providing an invalid rseq_cs pointer during registration, leading to a denial of service.
- 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-2025-38067?
CVE-2025-38067 is a medium-severity vulnerability in Debian Debian Linux, published on 18 Jun 2025. 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:
rseq: Fix segfault on registration when rseq_cs is non-zero
The rseq_cs field is documented as being set to 0 by user-space prior to registration, however this is not currently enforced by the kernel. This can result in a segfault on return to user-space if the value stored in the rseq_cs field doesn't point to a valid struct rseq_cs.
The correct solution to this would be to fail the rseq registration when the rseq_cs field is non-zero. However, some older versions of glibc will reuse the rseq area of previous threads without clearing the rseq_cs field and will also terminate the process if the rseq registration fails in a secondary thread. This wasn't caught in testing because in this case the leftover rseq_cs does point to a valid struct rseq_cs.
What we can do is clear the rseq_cs field on registration when it's non-zero which will prevent segfaults on registration and won't break the glibc versions that reuse rseq areas on thread creation.
Which versions are affected by CVE-2025-38067?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-38067?
Apply the vendor's patch.
Is CVE-2025-38067 being exploited?
There is no known exploitation of CVE-2025-38067 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as AZL-63977, AZL-72710, BELL-CVE-2025-38067, DEBIAN-CVE-2025-38067, GHSA-627j-hqc4-995q, ROOT-OS-DEBIAN-11-CVE-2025-38067 and 4 more.