# CVE-2016-10013: Xen privilege escalation via SYSCALL singlestep emulation

Source: https://junglewise.ai/threats/cve-2016-10013-xen-privilege-escalation-via-syscall-singlestep-emulation  
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-2016-10013 · Severity: high · CVSS 7.8 · Published 2017-01-26

A vulnerability in the Xen virtualization software could allow a user on a guest virtual machine to gain administrative control over that guest's operating system. This occurs due to a technical error in how the software handles specific processor instructions during emulation. While this allows for privilege escalation within the virtual machine, it does not inherently allow an attacker to escape to the host system or access other customers' data.

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

## Quick answers

**Is CVE-2016-10013 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-10013 being exploited in the wild.

**How severe is CVE-2016-10013?** High severity, with a CVSS score of 7.8, published 26 January 2017.

**Which products and versions are affected?** Xen Project Xen through 4.8.x.

**Is there a fix for CVE-2016-10013?** A patch was published on 2017-05-09: Debian security update released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2016-10013 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2016-10013?** 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 privilege escalation vulnerability exists in the Xen x86 instruction emulator's handling of the SYSCALL instruction. The emulator incorrectly raises singlestep (#DB) exceptions based on processor flags present at the start of the instruction rather than the end, deviating from expected hardware behavior for SYSCALL. An unprivileged user in a 64-bit x86 HVM guest can exploit this logic error to trigger an unexpected exception frame, potentially leading to kernel-level privilege escalation within the guest. The vulnerability is most prominent in Xen 4.6 and earlier; in version 4.7 and later, it typically requires specific non-default CPUID configurations or existing hardware access privileges. Linux guests are generally mitigated if they use an Interrupt Stack Table (IST) for #DB handling. Patches are available for supported Xen versions (XSA-204).

## Affected products

- Xen Project Xen through 4.8.x

## Timeline

- 2016-12-19: advisory: XSA-204 released by Xen Project
- 2017-01-26: disclosed: NVD publication date
- 2017-05-09: patched: Debian security update released

## References

- [http://www.debian.org/security/2017/dsa-3847](http://www.debian.org/security/2017/dsa-3847)
- [http://www.securityfocus.com/bid/94963](http://www.securityfocus.com/bid/94963)
- [http://www.securitytracker.com/id/1037491](http://www.securitytracker.com/id/1037491)
- [http://xenbits.xen.org/xsa/advisory-204.html](http://xenbits.xen.org/xsa/advisory-204.html)

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