---
title: "CVE-2016-2856\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-2016-2856?format=md
keywords: index, follow
---

# CVE-2016-2856

Publication date 13 March 2016

Last updated 25 August 2025

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**8.4 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2016-2856?format=md#impact-score)

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## Description

pt\_chown in the glibc package before 2.19-18+deb8u4 on Debian jessie; the
elibc package before 2.15-0ubuntu10.14 on Ubuntu 12.04 LTS and before
2.19-0ubuntu6.8 on Ubuntu 14.04 LTS; and the glibc package before
2.21-0ubuntu4.2 on Ubuntu 15.10 and before 2.23-0ubuntu1 on Ubuntu 16.04
LTS and 16.10 lacks a namespace check associated with file-descriptor
passing, which allows local users to capture keystrokes and spoof data, and
possibly gain privileges, via pts read and write operations, related to
debian/sysdeps/linux.mk. NOTE: this is not considered a vulnerability in
the upstream GNU C Library because the upstream documentation has a clear
security recommendation against the --enable-pt\_chown option.

### From the Ubuntu Security Team

Martin Carpenter discovered that pt\_chown in the GNU C Library
did not properly check permissions for tty files. A local attacker
could use this to gain administrative privileges or expose sensitive
information.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| eglibc | 17.04 zesty | Not in release |
| 16.10 yakkety | Not in release |
| 16.04 LTS xenial | Not in release |
| 15.10 wily | Not in release |
| 14.04 LTS trusty | Fixed 2.19-0ubuntu6.8 |
| 12.04 LTS precise | Fixed 2.15-0ubuntu10.14 |
| glibc | 17.04 zesty | Not affected |
| 16.10 yakkety | Not affected |
| 16.04 LTS xenial | Not affected |
| 15.10 wily | Fixed 2.21-0ubuntu4.2 |
| 14.04 LTS trusty | Not in release |
| 12.04 LTS precise | 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)
* [Patch details](https://ubuntu.com/security/CVE-2016-2856?format=md#patch-details)

### Patch details

For informational purposes only. We recommend not to cherry-pick updates. [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)

| Package | Patch details |
| --- | --- |
| glibc | * Upstream:   <https://sourceware.org/git/?p=glibc.git;a=commit;h=77356912e83601fd0240d22fe4d960348b82b5c3> |

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

8.4 · High

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 8.4 · High |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-2856)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2016-2856)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2016-2856)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2016-2856)

### Related Ubuntu Security Notices (USN)

+ [USN-2985-1](https://usn.ubuntu.com/USN-2985-1)
+ GNU C Library vulnerabilities
+ 25 May 2016

### Other references

* <http://anonscm.debian.org/cgit/pkg-glibc/glibc.git/commit/?h=jessie&id=09f7764882a81e13e7b5d87d715412283a6ce403>
* <http://anonscm.debian.org/cgit/pkg-glibc/glibc.git/commit/?h=jessie&id=11475c083282c1582c4dd72eecfcb2b7d308c958>
* <http://www.openwall.com/lists/oss-security/2016/03/07/2>
* <https://www.cve.org/CVERecord?id=CVE-2016-2856>