Linux Kernel: Xen sys-hypervisor Buffer Overflow (CVE-2026-31786)
CVE-2026-31786 Published on April 30, 2026
Buffer overflow in drivers/xen/sys-hypervisor.c
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
Products Associated with CVE-2026-31786
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Affected Versions
Linux:- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below e3af585e1728c917682b6a3de9a69b41fb9194d4 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 8288d031a01dbacfde3fc643f7be3d23504de64d is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below f458ba102da97fafca106327086fc95f3fc764cb is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 4b4defd2fce3f966c25adabf46644a85558f1169 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below d5f59216650c51e5e3fcb7517c825bc8047f60ef is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 52cecff98bda2c51eed1c6ce9d21c5d6268fb19d is affected.
- Version 5.10.254, <= 5.10.* is unaffected.
- Version 5.15.204, <= 5.15.* is unaffected.
- Version 6.1.170, <= 6.1.* is unaffected.
- Version 6.6.137, <= 6.6.* is unaffected.
- Version 6.12.85, <= 6.12.* is unaffected.
- Version 6.18.26, <= 6.18.* is unaffected.
- Version 7.0.3, <= 7.0.* is unaffected.