# CVE-2016-10024: Xen denial of service via instruction stream modification in x86 PV guests

Source: https://junglewise.ai/threats/cve-2016-10024-xen-denial-of-service-via-instruction-stream-modification-in-x86  
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-2016-10024 · Severity: medium · CVSS 6 · Published 2017-01-26

Xen is a hypervisor used to run multiple virtual machines on a single physical server. A vulnerability in how it handles certain guest operations allows a malicious administrator of a virtual machine to crash or freeze the entire physical host. This results in a total service outage for all other virtual machines running on that same hardware.

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-2016-10024 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-10024 being exploited in the wild.

**How severe is CVE-2016-10024?** Medium severity, with a CVSS score of 6, 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 through 4.8.x.

**Is there a fix for CVE-2016-10024?** A patch was published on 2016-12-21: Patches released for Xen unstable and stable branches Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2016-10024 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2016-10024?** 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 vulnerability exists in Xen's x86 instruction emulator when handling Paravirtualized (PV) guest operations, such as page table writes. A malicious guest kernel administrator can asynchronously modify the instruction stream during emulation to manipulate the EFLAGS.IF bit. This allows the guest to mask interrupts in a way that the hypervisor does not expect, leading to a host-level hang or crash (Denial of Service). The issue specifically affects x86 PV guests; HVM and ARM guests are not impacted. Patches have been released by the Xen Project (XSA-202) and various downstream vendors like Citrix and Debian.

## Affected products

- Xen Project Xen 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-202
- 2016-12-21: patched: Patches released for Xen unstable and stable branches
- 2017-01-26: disclosed: NVD publication date

## References

- [http://www.debian.org/security/2017/dsa-3847](http://www.debian.org/security/2017/dsa-3847)
- [http://www.securityfocus.com/bid/95021](http://www.securityfocus.com/bid/95021)
- [http://www.securitytracker.com/id/1037517](http://www.securitytracker.com/id/1037517)
- [http://xenbits.xen.org/xsa/advisory-202.html](http://xenbits.xen.org/xsa/advisory-202.html)
- [https://security.gentoo.org/glsa/201612-56](https://security.gentoo.org/glsa/201612-56)
- [https://support.citrix.com/article/CTX219378](https://support.citrix.com/article/CTX219378)

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