---
title: "CVE-2016-0739\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-2016-0739?format=md
keywords: index, follow
---

# CVE-2016-0739

Publication date 23 February 2016

Last updated 25 August 2025

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**5.9 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2016-0739?format=md#impact-score)

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## Description

libssh before 0.7.3 improperly truncates ephemeral secrets generated for
the (1) diffie-hellman-group1 and (2) diffie-hellman-group14 key exchange
methods to 128 bits, which makes it easier for man-in-the-middle attackers
to decrypt or intercept SSH sessions via unspecified vectors, aka a
"bits/bytes confusion bug."

[Read the notes from the security team](https://ubuntu.com/security/CVE-2016-0739?format=md#notes)

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| libssh | 16.10 yakkety | Fixed 0.6.3-4.2ubuntu1 |
| 16.04 LTS xenial | Fixed 0.6.3-4.2ubuntu1 |
| 15.10 wily | Fixed 0.6.3-3ubuntu3.2 |
| 14.04 LTS trusty | Fixed 0.6.1-0ubuntu3.3 |
| 12.04 LTS precise | Fixed 0.5.2-1ubuntu0.12.04.6 |

---

* [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)

affects "all versions of libssh 0.1 and later"

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

5.9 · Medium

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 5.9 · Medium |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-0739)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2016-0739)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2016-0739)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2016-0739)

### Related Ubuntu Security Notices (USN)

+ [USN-2912-1](https://usn.ubuntu.com/USN-2912-1)
+ libssh vulnerabilities
+ 23 February 2016

### Other references

* <https://www.libssh2.org/adv_20160223.html>
* <https://www.libssh.org/2016/02/23/libssh-0-7-3-security-and-bugfix-release/>
* <https://www.cve.org/CVERecord?id=CVE-2016-0739>