CVE-2025-38067

/// Technical 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 r

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References