CVE-2025-38067: debian linux — Fix

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.

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected Products

Vendor	Product	Versions
linux	linux_kernel	4.18 — 5.10.240
linux	linux_kernel	5.11 — 5.15.189
linux	linux_kernel	5.16 — 6.1.146
linux	linux_kernel	6.2 — 6.6.99
linux	linux_kernel	6.7 — 6.12.39
linux	linux_kernel	6.13 — 6.14.9
debian	debian_linux	All

References

Advisories & Patches

https://git.kernel.org/stable/c/2df285dab00fa03a3ef939b6cb0d0d0aeb0791db https://git.kernel.org/stable/c/3e4028ef31b69286c9d4878cee0330235f53f218 https://git.kernel.org/stable/c/48900d839a3454050fd5822e34be8d54c4ec9b86 https://git.kernel.org/stable/c/b2b05d0dc2f4f0646922068af435aed5763d16ba https://git.kernel.org/stable/c/eaf112069a904b6207b4106ff083e0208232a2eb https://git.kernel.org/stable/c/f004f58d18a2d3dc761cf973ad27b4a5997bd876 https://git.kernel.org/stable/c/fd881d0a085fc54354414aed990ccf05f282ba53

Other References

https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html https://cert-portal.siemens.com/productcert/html/ssa-082556.html

Frequently Asked Questions

What is CVE-2025-38067? +

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. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-38067? +

CVE-2025-38067 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-38067? +

CVE-2025-38067 affects products from debian, linux, specifically: debian_linux, linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-38067? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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