Loading vulnerability…
CVE-2026-31786 is a Linux kernel vulnerability in drivers/xen/sys-hypervisor.c affecting Xen-related sysfs exposure of the hypervisor build ID. The flaw is in the code path that handles the build ID returned by HYPERVISOR_xen_version(XENVER_build_id) and exposes it through the buildid sysfs attribute. That build ID is binary data, typically 16 or 20 bytes, and is not NUL-terminated. The vulnerable implementation used sprintf() in buildid_show as though the returned value were a C string, causing the kernel to continue reading beyond the intended build ID buffer until a zero byte was encountered. This results in an out-of-bounds read and was described in some advisories as a buffer overflow condition in the sysfs handling code. In rare cases, the faulty write path may also extend past the sysfs buffer boundary. The upstream fix replaces sprintf() with memcpy() so the build ID is copied as raw bytes with the correct length.
Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
If you can’t patch tonight, do this now.
Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
17 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Linux kernel buffer overflow vulnerability in drivers/xen/sys-hypervisor.c.
A Linux kernel buffer overflow vulnerability in drivers/xen/sys-hypervisor.c.
A Linux kernel buffer overflow vulnerability in drivers/xen/sys-hypervisor.c.
A buffer overflow vulnerability in the Linux kernel's drivers/xen/sys-hypervisor.c, where the build ID returned by HYPERVISOR_xen_version(XENVER_build_id) is not NUL-terminated and sprintf in buildid_show can over-read and copy until a NUL is found.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.