---
title: "CVE-2017-8900\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-2017-8900?format=md
keywords: index, follow
---

# CVE-2017-8900

Publication date 11 May 2017

Last updated 25 August 2025

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**4.6 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2017-8900?format=md#impact-score)

Toggle side navigation

## Description

LightDM through 1.22.0, when systemd is used in Ubuntu 16.10 and 17.x,
allows physically proximate attackers to bypass intended AppArmor
restrictions and visit the home directories of arbitrary users by
establishing a guest session.

[Read the notes from the security team](https://ubuntu.com/security/CVE-2017-8900?format=md#notes)

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| lightdm | 17.04 zesty | Fixed 1.22.0-0ubuntu2.1 |
| 16.10 yakkety | Fixed 1.19.5-0ubuntu1.2 |
| 16.04 LTS xenial | Not affected |
| 14.04 LTS trusty | Not in release |

---

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

## Notes

---

### [tyhicks](https://launchpad.net/~tyhicks)

This issue was introduced when the user session handling moved from
upstart to systemd in Ubuntu 16.10.

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

4.6 · Medium

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 4.6 · Medium |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-8900)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2017-8900)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2017-8900)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2017-8900)

### Related Ubuntu Security Notices (USN)

+ [USN-3285-1](https://usn.ubuntu.com/USN-3285-1)
+ LightDM vulnerability
+ 12 May 2017

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2017-8900>