# CVE-2016-9380: Xen pygrub arbitrary file read and deletion via delimiter injection

Source: https://junglewise.ai/threats/cve-2016-9380-xen-pygrub-arbitrary-file-read-and-deletion-via-delimiter  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2017-01-23. Updated: 2026-05-13  
License: CC BY 4.0 with a link back

CVE-2016-9380 · Severity: high · CVSS 7.5 · Published 2017-01-23

A vulnerability in the Xen virtualization platform's boot loader emulator, pygrub, allows a guest administrator to access or delete files on the host server. By manipulating the boot configuration, an attacker can trick the host system into treating sensitive files as part of the guest's startup process. This can lead to the theft of private host data or a complete system disruption if critical host files are deleted.

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-2016-9380 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-9380 being exploited in the wild.

**How severe is CVE-2016-9380?** High severity, with a CVSS score of 7.5, published 23 January 2017.

**Which products and versions are affected?** Citrix Xenserver 6.0.2, 6.2.0, 6.5, 7.0; Xen Project Xen 2.0 and later.

**Is there a fix for CVE-2016-9380?** A patch was published on 2016-11-22: Patch released by Xen Project Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2016-9380 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2016-9380?** 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 delimiter injection vulnerability exists in the pygrub boot loader emulator when nul-delimited output format is requested. The toolstack (libxl) fails to properly sanitize or quote output from pygrub, allowing an attacker with guest administrator privileges to inject NUL bytes into the bootloader configuration file. This causes libxl to misinterpret the output, potentially treating any host file as the guest's initial ramdisk. Consequently, the attacker can read the contents of host files or cause the toolstack to delete them during the boot process. The vulnerability affects systems using xl, libxl, or libvirt where guests are configured to use pygrub.

## Affected products

- Xen Project Xen 2.0 and later
- Citrix XenServer 6.0.2, 6.2.0, 6.5, 7.0

## Timeline

- 2016-11-22: disclosed: Initial public release of XSA-198
- 2016-11-22: patched: Patch released by Xen Project
- 2017-01-23: advisory: NVD publication date

## References

- [http://www.securityfocus.com/bid/94473](http://www.securityfocus.com/bid/94473)
- [http://www.securitytracker.com/id/1037347](http://www.securitytracker.com/id/1037347)
- [http://xenbits.xen.org/xsa/advisory-198.html](http://xenbits.xen.org/xsa/advisory-198.html)
- [http://xenbits.xen.org/xsa/xsa198.patch](http://xenbits.xen.org/xsa/xsa198.patch)
- [https://security.gentoo.org/glsa/201612-56](https://security.gentoo.org/glsa/201612-56)
- [https://support.citrix.com/article/CTX218775](https://support.citrix.com/article/CTX218775)

## 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)