GHSA-627J-HQC4-995Q

Vulnerability from github – Published: 2025-06-18 12:30 – Updated: 2026-05-12 15:30
VLAI
Details

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.

Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2025-38067"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-06-18T10:15:39Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nrseq: Fix segfault on registration when rseq_cs is non-zero\n\nThe rseq_cs field is documented as being set to 0 by user-space prior to\nregistration, however this is not currently enforced by the kernel. This\ncan result in a segfault on return to user-space if the value stored in\nthe rseq_cs field doesn\u0027t point to a valid struct rseq_cs.\n\nThe correct solution to this would be to fail the rseq registration when\nthe rseq_cs field is non-zero. However, some older versions of glibc\nwill reuse the rseq area of previous threads without clearing the\nrseq_cs field and will also terminate the process if the rseq\nregistration fails in a secondary thread. This wasn\u0027t caught in testing\nbecause in this case the leftover rseq_cs does point to a valid struct\nrseq_cs.\n\nWhat we can do is clear the rseq_cs field on registration when it\u0027s\nnon-zero which will prevent segfaults on registration and won\u0027t break\nthe glibc versions that reuse rseq areas on thread creation.",
  "id": "GHSA-627j-hqc4-995q",
  "modified": "2026-05-12T15:30:53Z",
  "published": "2025-06-18T12:30:33Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38067"
    },
    {
      "type": "WEB",
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2df285dab00fa03a3ef939b6cb0d0d0aeb0791db"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3e4028ef31b69286c9d4878cee0330235f53f218"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/48900d839a3454050fd5822e34be8d54c4ec9b86"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b2b05d0dc2f4f0646922068af435aed5763d16ba"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/eaf112069a904b6207b4106ff083e0208232a2eb"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f004f58d18a2d3dc761cf973ad27b4a5997bd876"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fd881d0a085fc54354414aed990ccf05f282ba53"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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