# CVE-2016-10025: Xen VMFUNC emulation NULL pointer dereference on AMD SVM

Source: https://junglewise.ai/threats/cve-2016-10025-xen-vmfunc-emulation-null-pointer-dereference-on-amd-svm  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2017-01-26. Updated: 2026-05-13  
License: CC BY 4.0 with a link back

CVE-2016-10025 · Severity: medium · CVSS 5.5 · Published 2017-01-26

A vulnerability in the Xen hypervisor, which is software used to run multiple virtual machines on a single physical server, could allow a user on a guest virtual machine to crash the entire host system. This issue specifically affects servers using AMD processors. An exploit would result in a total service outage for all virtual machines running on that physical hardware, though it does not allow for data theft.

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

## Quick answers

**Is CVE-2016-10025 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-10025 being exploited in the wild.

**How severe is CVE-2016-10025?** Medium severity, with a CVSS score of 5.5, published 26 January 2017.

**Which products and versions are affected?** Citrix Xenserver 6.0.2, 6.2.0, 6.5, 7.0; Xen Project Xen 4.6.x through 4.8.x.

**Is there a fix for CVE-2016-10025?** A patch was published on 2016-12-21. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2016-10025 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2016-10025?** Check whether you run Citrix Xenserver or 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 NULL pointer dereference vulnerability exists in Xen versions 4.6.x through 4.8.x during the emulation of the Intel VMX VMFUNC leaf 0 instruction. While the hvmemul_vmfunc function pointer was introduced for Intel hardware, the pointer remains NULL on AMD SVM hardware. The hypervisor fails to perform a NULL check before an indirect function call at the call site. A local attacker with privileges in an HVM guest can trigger this missing check to cause a hypervisor panic, leading to a denial of service. This issue only affects HVM guests running on AMD x86 hardware; PV guests and Intel-based systems are not impacted. Patches are available from the Xen Project (XSA-203).

## Affected products

- Xen Project Xen 4.6.x through 4.8.x
- Citrix XenServer 6.0.2, 6.2.0, 6.5, 7.0

## Timeline

- 2016-12-21: advisory: Xen Project released XSA-203
- 2016-12-21: patched
- 2017-01-26: disclosed: NVD publication date

## References

- [http://www.securityfocus.com/bid/95026](http://www.securityfocus.com/bid/95026)
- [http://www.securitytracker.com/id/1037518](http://www.securitytracker.com/id/1037518)
- [http://xenbits.xen.org/xsa/advisory-203.html](http://xenbits.xen.org/xsa/advisory-203.html)
- [https://support.citrix.com/article/CTX219378](https://support.citrix.com/article/CTX219378)

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