Linux Kernel Vulnerability Affecting User-Space Registration

CVE-2025-38067

What is CVE-2025-38067?

A vulnerability in the Linux kernel related to the rseq (restartable sequences) functionality can lead to segmentation faults during the registration process. Specifically, the rseq_cs field is meant to be set to zero by user-space prior to registration, but current kernel implementations do not enforce this rule. As a result, if a non-zero value is stored, it may not point to a valid struct rseq_cs, possibly causing a segmentation fault upon return to user-space. This issue is compounded in older versions of glibc, which may not clear the rseq_cs field when reusing rseq areas across threads, thereby increasing the risk of process termination. To resolve this, the registration process should enforce a check for a non-zero rseq_cs field, ensuring that invalid pointers are not utilized, thus maintaining system integrity.

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