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…
Does this matter?
Lower severity and a low EPSS score (0.52%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 5.5 MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.52% probability · 43th percentile
- CISA KEV
- Not listed
- Affected
- linux/linux kernel · debian/debian linux
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/2df285dab00fa03a3ef939b6cb0d0d0aeb0791dbPatch
- https://git.kernel.org/stable/c/3e4028ef31b69286c9d4878cee0330235f53f218Patch
- https://git.kernel.org/stable/c/48900d839a3454050fd5822e34be8d54c4ec9b86Patch
- https://git.kernel.org/stable/c/b2b05d0dc2f4f0646922068af435aed5763d16baPatch
- https://git.kernel.org/stable/c/eaf112069a904b6207b4106ff083e0208232a2ebPatch
- https://git.kernel.org/stable/c/f004f58d18a2d3dc761cf973ad27b4a5997bd876Patch
- https://git.kernel.org/stable/c/fd881d0a085fc54354414aed990ccf05f282ba53Patch
- https://lists.debian.org/debian-lts-announce/2025/10/msg00007.htmlThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.htmlThird Party Advisory
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.