---
title: "CVE-2017-12855\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2017-12855?format=md
keywords: index, follow
---

# CVE-2017-12855

Publication date 15 August 2017

Last updated 25 August 2025

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**6.5 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2017-12855?format=md#impact-score)

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## Description

Xen maintains the \_GTF\_{read,writ}ing bits as appropriate, to inform the
guest that a grant is in use. A guest is expected not to modify the grant
details while it is in use, whereas the guest is free to modify/reuse the
grant entry when it is not in use. Under some circumstances, Xen will clear
the status bits too early, incorrectly informing the guest that the grant
is no longer in use. A guest may prematurely believe that a granted frame
is safely private again, and reuse it in a way which contains sensitive
information, while the domain on the far end of the grant is still using
the grant. Xen 4.9, 4.8, 4.7, 4.6, and 4.5 are affected.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| xen | 17.04 zesty | Fixed 4.8.0-1ubuntu2.4 |
| 16.04 LTS xenial | Fixed 4.6.5-0ubuntu1.4 |
| 14.04 LTS trusty | Fixed 4.4.2-0ubuntu0.14.04.14 |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

6.5 · Medium

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Local |
  | Attack complexity | Low |
  | Privileges required | Low |
  | User interaction | None |
  | Scope | Changed |
  | Confidentiality impact | High |
  | Integrity impact | None |
  | Availability impact | None |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 6.5 · Medium |
  | Exploitability score | - |
  | Impact score | - |

**Vector:** CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-12855)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2017-12855)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2017-12855)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2017-12855)

### Other references

* <https://xenbits.xen.org/xsa/advisory-230.html>
* <https://www.cve.org/CVERecord?id=CVE-2017-12855>