CVE-2026-31786

Summary

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

Affected Software

Weaknesses

ADP Enrichment

CVE Program Container

Additional References

• http://www.openwall.com/lists/oss-security/2026/04/28/12
• http://xenbits.xen.org/xsa/advisory-485.html

References

• https://git.kernel.org/stable/c/e3af585e1728c917682b6a3de9a69b41fb9194d4
• https://git.kernel.org/stable/c/8288d031a01dbacfde3fc643f7be3d23504de64d
• https://git.kernel.org/stable/c/f458ba102da97fafca106327086fc95f3fc764cb
• https://git.kernel.org/stable/c/4b4defd2fce3f966c25adabf46644a85558f1169
• https://git.kernel.org/stable/c/5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a
• https://git.kernel.org/stable/c/d5f59216650c51e5e3fcb7517c825bc8047f60ef
• https://git.kernel.org/stable/c/52cecff98bda2c51eed1c6ce9d21c5d6268fb19d
• https://git.kernel.org/stable/c/27fdbab4221b375de54bf91919798d88520c6e28

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