CVE-2026-31786

high

Published 2026-04-30 · Modified 2026-05-06

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CVSS v3

7.8

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

CVSS v4 NEW

—

not yet in upstream

VIR risk

7.8

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

Predictions

Exploit likelihood

75%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

Mitigation details

Source: Debian Security Tracker · View original ↗ · DFSG

CVE-2026-31786 NameCVE-2026-31786 DescriptionIn 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…

CVE-2026-31786

Name	CVE-2026-31786
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
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
References	DLA-4561-1, DLA-4606-1, DSA-6238-1, DSA-6243-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
linux (PTS)	bullseye	5.10.223-1	vulnerable
	bullseye (security)	5.10.257-1	fixed
	bookworm	6.1.170-3	fixed
	bookworm (security)	6.1.174-1	fixed
	trixie	6.12.86-1	fixed
	trixie (security)	6.12.90-2	fixed
	forky, sid	7.0.10-1	fixed
linux-6.1 (PTS)	bullseye (security)	6.1.174-1~deb11u1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Origin
linux	source	bullseye	5.10.257-1	DLA-4606-1
linux	source	bookworm	6.1.170-1	DSA-6243-1
linux	source	trixie	6.12.85-1	DSA-6238-1
linux	source	(unstable)	7.0.3-1
linux-6.1	source	bullseye	6.1.170-1~deb11u1	DLA-4561-1

Notes

https://xenbits.xen.org/xsa/advisory-485.html

Home - Debian Security - Source (Git)

Apply commands

text fix

Notes

https://xenbits.xen.org/xsa/advisory-485.html

OS impact

Linux kernel Affected 2 releases

Version	Status	Fixed in
7.1	Affected	—
—	Affected	`5.10.254`

SUSE Affected 1 release

Version	Status	Fixed in
—	Affected	—

Debian Fixed 5 releases

Version	Status	Fixed in
trixie	Fixed	`6.12.85-1`
sid	Fixed	`7.0.3-1`
forky	Fixed	`7.0.3-1`
bullseye	Fixed	`6.1.170-1~deb11u1`
bookworm	Fixed	`6.1.170-1`

References

CWEs

CWE-787

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.