---
title: "CVE-2016-5420\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-2016-5420?format=md
keywords: index, follow
---

# CVE-2016-5420

Publication date 3 August 2016

Last updated 25 August 2025

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**7.5 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2016-5420?format=md#impact-score)

Toggle side navigation

## Description

curl and libcurl before 7.50.1 do not check the client certificate when
choosing the TLS connection to reuse, which might allow remote attackers to
hijack the authentication of the connection by leveraging a previously
created connection with a different client certificate.

[Read the notes from the security team](https://ubuntu.com/security/CVE-2016-5420?format=md#notes)

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| curl | 17.04 zesty | Not affected |
| 16.10 yakkety | Not affected |
| 16.04 LTS xenial | Fixed 7.47.0-1ubuntu2.1 |
| 14.04 LTS trusty | Fixed 7.35.0-1ubuntu2.8 |
| 12.04 LTS precise | Fixed 7.22.0-3ubuntu4.16 |

---

* [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-2016-5420?format=md#patch-details)

## Notes

---

### [seth-arnold](https://launchpad.net/~seth-arnold)

when built against NSS another patch is needed, see
http://www.openwall.com/lists/oss-security/2016/09/05/1 for information
http://www.openwall.com/lists/oss-security/2016/09/05/7

### 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 |
| --- | --- |
| curl | * Upstream:   <https://curl.haxx.se/CVE-2016-5420.patch> |

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

7.5 · High

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 7.5 · High |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-5420)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2016-5420)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2016-5420)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2016-5420)

### Related Ubuntu Security Notices (USN)

+ [USN-3048-1](https://usn.ubuntu.com/USN-3048-1)
+ curl vulnerabilities
+ 8 August 2016

### Other references

* <https://curl.haxx.se/docs/adv_20160803B.html>
* <http://www.openwall.com/lists/oss-security/2016/09/05/1>
* <https://www.cve.org/CVERecord?id=CVE-2016-5420>