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CVE-2026-31786

7.8 · 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…

Published Apr 30, 2026CWE-787EPSS 0.21%

Overview

CVE-2026-31786 is a high-severity vulnerability. It was published on April 30, 2026 and has a CVSS 3.1 base score of 7.8 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

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

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/27fdbab4221b375de54bf91919798d88520c6e28Refgit.kernel.org/stable/c/4b4defd2fce3f966c25adabf46644a85558f1169Refgit.kernel.org/stable/c/52cecff98bda2c51eed1c6ce9d21c5d6268fb19dRefgit.kernel.org/stable/c/5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0aRefgit.kernel.org/stable/c/8288d031a01dbacfde3fc643f7be3d23504de64dRefgit.kernel.org/stable/c/d5f59216650c51e5e3fcb7517c825bc8047f60efRefgit.kernel.org/stable/c/e3af585e1728c917682b6a3de9a69b41fb9194d4Refgit.kernel.org/stable/c/f458ba102da97fafca106327086fc95f3fc764cbRefwww.openwall.com/lists/oss-security/2026/04/28/12Refxenbits.xen.org/xsa/advisory-485.html

How CyberStrike helps

Frequently asked questions

What is CVE-2026-31786?

CVE-2026-31786 is a high-severity vulnerability. It was published on April 30, 2026 and has a CVSS 3.1 base score of 7.8 (HIGH).

How severe is CVE-2026-31786?

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-31786?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-31786?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-31786 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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