CVE-2026-31786

High

In the Linux kernel, the following vulnerability has been resolved: Buffer overflow in drivers/xen/sys-hypervisor.c The build id returned by HYPERVISOR_xen_version(XENVER_build_id) is neither NUL terminated nor a string. The first causes a buffer overflow as sprintf in buildid_show will read and copy till it finds a NUL. 00000000 f4 91 51 f4 dd 38 9e 9d 65 47 52 eb 10 71 db 50 |..Q..8..eGR..q.P| 00000010 b9 a8 01 42 6f 2e 32 |...Bo.2| 00000017 So use a memcpy instead of sprintf to have the correct value: 00000000 f4 91 51 f4 dd 00 9e 9d 65 47 52 eb 10 71 db 50 |..Q.....eGR..q.P| 00000010 b9 a8 01 42 |...B| 00000014 (the above have a hack to embed a zero inside and check it's returned correctly). This is XSA-485 / CVE-2026-31786

Package Linux Kernel
Published 2026-04-30
Last modified 2026-05-06
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

7.8

out of 10
High
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness type

CWE-787

CVE-2026-31786 is a Out-of-bounds Write vulnerability

What is Out-of-bounds Write?

The product writes data past the end or before the beginning of the intended buffer. Learn more on MITRE CWE

Affected versions

Linux kernel versions 4.13 and later are affected. Fixed in 5.10.254, 5.15.204, 6.1.170, 6.6.137, 6.12.85, 6.18.26, 7.0.3, 7.1-rc2 and their respective stable series.

Affected from
≥ 4.13
Fixed in
✓ 5.10.254 5.10.x ✓ 5.15.204 5.15.x ✓ 6.1.170 6.1.x ✓ 6.6.137 6.6.x ✓ 6.12.85 6.12.x ✓ 6.18.26 6.18.x ✓ 7.0.3 7.0.x ✓ 7.1-rc2

References

The following references provide additional information about CVE-2026-31786 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

8 patch commits total View all on NVD

Frequently asked questions

  • What is CVE-2026-31786?

    CVE-2026-31786 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10 , classified as an Out-of-bounds Write flaw (CWE-787) . It affects Linux kernel versions from 4.13 onward and has been patched in 5.10.254, 5.15.204, 6.1.170 and others. CVE-2026-31786 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2026-31786?

    CVE-2026-31786 has a CVSS score of 7.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H .

  • Is there a patch available for CVE-2026-31786?

    Yes — CVE-2026-31786 has been patched. Fixed versions include 5.10.254, 5.15.204, 6.1.170 and others. If you are running Linux kernel 4.13 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2026-31786 actively exploited?

    No — CVE-2026-31786 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

  • What is Out-of-bounds Write (CWE-787)?

    The product writes data past the end or before the beginning of the intended buffer. View CWE-787 on MITRE CWE →

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