CVE-2026-31786

Buffer overflow in drivers/xen/sys-hypervisor.c

State: Published
Severity: 7.8 High
Published: Apr 30, 2026
Updated: Oct 19, 2026
Reserved: Mar 9, 2026

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

Scores

CVSS	Score	Vector	Source
3.1	7.8 High	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H	Linux

Weaknesses

CWE-120 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

Affected Products

Product	Versions
LinuxLinux	84b7625728ea311ea35bdaa0eded53c1c56baeaa to before e3af585e1728c917682b6a3de9a69b41fb9194d4Affected 84b7625728ea311ea35bdaa0eded53c1c56baeaa to before 8288d031a01dbacfde3fc643f7be3d23504de64dAffected 84b7625728ea311ea35bdaa0eded53c1c56baeaa to before f458ba102da97fafca106327086fc95f3fc764cbAffected 84b7625728ea311ea35bdaa0eded53c1c56baeaa to before 4b4defd2fce3f966c25adabf46644a85558f1169Affected 84b7625728ea311ea35bdaa0eded53c1c56baeaa to before 5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0aAffected 84b7625728ea311ea35bdaa0eded53c1c56baeaa to before d5f59216650c51e5e3fcb7517c825bc8047f60efAffected 84b7625728ea311ea35bdaa0eded53c1c56baeaa to before 52cecff98bda2c51eed1c6ce9d21c5d6268fb19dAffected 84b7625728ea311ea35bdaa0eded53c1c56baeaa to before 27fdbab4221b375de54bf91919798d88520c6e28Affected
LinuxLinux	4.13Affected before 4.13Not affected 5.10.254 through 5.10.Not affected 5.15.204 through 5.15.Not affected 6.1.170 through 6.1.Not affected 6.6.137 through 6.6.Not affected 6.12.85 through 6.12.Not affected 6.18.26 through 6.18.Not affected 7.0.3 through 7.0.*Not affected 7.1 and laterNot affected

Product

Versions

LinuxLinux

84b7625728ea311ea35bdaa0eded53c1c56baeaa to before e3af585e1728c917682b6a3de9a69b41fb9194d4Affected
84b7625728ea311ea35bdaa0eded53c1c56baeaa to before 8288d031a01dbacfde3fc643f7be3d23504de64dAffected
84b7625728ea311ea35bdaa0eded53c1c56baeaa to before f458ba102da97fafca106327086fc95f3fc764cbAffected
84b7625728ea311ea35bdaa0eded53c1c56baeaa to before 4b4defd2fce3f966c25adabf46644a85558f1169Affected
84b7625728ea311ea35bdaa0eded53c1c56baeaa to before 5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0aAffected
84b7625728ea311ea35bdaa0eded53c1c56baeaa to before d5f59216650c51e5e3fcb7517c825bc8047f60efAffected
84b7625728ea311ea35bdaa0eded53c1c56baeaa to before 52cecff98bda2c51eed1c6ce9d21c5d6268fb19dAffected
84b7625728ea311ea35bdaa0eded53c1c56baeaa to before 27fdbab4221b375de54bf91919798d88520c6e28Affected

LinuxLinux

4.13Affected
before 4.13Not affected
5.10.254 through 5.10.*Not affected
5.15.204 through 5.15.*Not affected
6.1.170 through 6.1.*Not affected
6.6.137 through 6.6.*Not affected
6.12.85 through 6.12.*Not affected
6.18.26 through 6.18.*Not affected
7.0.3 through 7.0.*Not affected
7.1 and laterNot affected

References

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