Overview
About vulnerability
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
Details
- Affected product:
- AlmaLinux 9.2 ESU , TuxCare 9.6 ESU
- Affected packages:
- kernel @ 5.14.0 (+1 more)
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