# CVE-2026-62431: Xen Viridian STIMER division by zero denial of service

Source: https://junglewise.ai/threats/cve-2026-62431-xen-viridian-stimer-division-by-zero-denial-of-service  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-28. Updated: 2026-07-28  
License: CC BY 4.0 with a link back

CVE-2026-62431 · Severity: info · CVSS 6.8 · Published 2026-07-28

A vulnerability exists in the Xen hypervisor, which is software used to run multiple virtual machines on a single physical server. An attacker controlling a virtual machine could exploit a flaw in how the system handles specific timer functions to crash the entire physical host server. This results in a total denial of service, causing all other virtual machines on that server to stop functioning.

Technologies: [Xen Project Xen](https://junglewise.ai/threats/technologies/xen). Vendors: [Xen Project](https://junglewise.ai/threats/vendors/xen-project).

## Quick answers

**Is CVE-2026-62431 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-62431 being exploited in the wild.

**How severe is CVE-2026-62431?** Informational severity, with a CVSS score of 6.8, published 28 July 2026.

**Which products and versions are affected?** Xen Project Xen 4.13 onwards.

**Is there a fix for CVE-2026-62431?** A patch was published on 2026-07-28. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-62431 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-62431?** Check whether you run Xen Project Xen at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A division-by-zero vulnerability exists in the Xen hypervisor's handling of Viridian STIMERs (Synthetic Timers). The flaw is located in the logic for periodic timers where a user-controlled divisor value is not properly validated before use in a division operation. An unprivileged HVM guest with Viridian STIMERs enabled can trigger a #DE (Divide Error) fault by setting the divisor to zero. Because this fault occurs within the hypervisor context, it leads to a crash of the entire host (Denial of Service). The vulnerability affects Xen versions 4.13 and later; versions 4.12 and earlier are unaffected. A patch is available from the Xen Project (XSA-504).

## Affected products

- Xen Project Xen 4.13 onwards

## Timeline

- 2026-07-28: disclosed
- 2026-07-28: advisory
- 2026-07-28: patched

## References

- [https://xenbits.xenproject.org/xsa/advisory-504.html](https://xenbits.xenproject.org/xsa/advisory-504.html)

## Related threats

- [Xen arbitrary read/write via grant copy caching](https://junglewise.ai/threats/cve-2026-102704-this-cna-information-record-relates-to-multiple-cves-the-text)
- [Xen hypervisor arbitrary read/write via grant copy](https://junglewise.ai/threats/cve-2026-102703-this-cna-information-record-relates-to-multiple-cves-the-text)
- [Xen VMX VMentry failure with branch tracing and blocked states](https://junglewise.ai/threats/cve-2026-79611-for-xsa-308-logic-was-introduced-as-vmx-vmentry-checks-do-not)
- [Xen XPTI privilege escalation on huge-memory systems](https://junglewise.ai/threats/cve-2026-79609-xpti-xen-page-table-isolation-was-introduced-to-mitigate-meltdown)
- [Xen ineffectual Zenbleed workaround on AMD x86](https://junglewise.ai/threats/cve-2026-79608-the-workaround-for-xsa-433-zenbleed-was-later-re-worked-to-better)