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Vulnerability record · CVE-2026-31786 · published 30 April 2026

CVE-2026-31786: Linux kernel out-of-bounds write vulnerability

Linux · Linux Kernel

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

7.8 CVSS 3.1 High EPSS 0.21% · top 90.0% CWE-787 · Out-of-bounds write
7.8CVSS 3.1 base score
0.21%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
10References
17 Jun 2026Last modified by NVD

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

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://git.kernel.org/stable/c/27fdbab4221b375de54bf91919798d88520c6e28 Patch
https://git.kernel.org/stable/c/4b4defd2fce3f966c25adabf46644a85558f1169 Patch
https://git.kernel.org/stable/c/52cecff98bda2c51eed1c6ce9d21c5d6268fb19d Patch
https://git.kernel.org/stable/c/5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a Patch
https://git.kernel.org/stable/c/8288d031a01dbacfde3fc643f7be3d23504de64d Patch
https://git.kernel.org/stable/c/d5f59216650c51e5e3fcb7517c825bc8047f60ef Patch
https://git.kernel.org/stable/c/e3af585e1728c917682b6a3de9a69b41fb9194d4 Patch
https://git.kernel.org/stable/c/f458ba102da97fafca106327086fc95f3fc764cb Patch
http://www.openwall.com/lists/oss-security/2026/04/28/12 Mailing ListThird Party Advisory
http://xenbits.xen.org/xsa/advisory-485.html Mailing ListThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2026-31786), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.