---
title: "CVE-2018-20721\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-2018-20721?format=md
keywords: index, follow
---

# CVE-2018-20721

Publication date 16 January 2019

Last updated 25 August 2025

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**9.8 · Critical**

[Score breakdown](https://ubuntu.com/security/CVE-2018-20721?format=md#impact-score)

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## Description

URI\_FUNC() in UriParse.c in uriparser before 0.9.1 has an out-of-bounds
read (in uriParse\*Ex\* functions) for an incomplete URI with an IPv6 address
containing an embedded IPv4 address, such as a "//[::44.1" address.

### From the Ubuntu Security Team

It was discovered that uriparser incorrectly handled certain URIs. An
attacker could use this vulnerability to cause a crash or possibly leak
sensitive information.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| uriparser | 22.04 LTS jammy | Not affected |
| 21.10 impish | Not affected |
| 21.04 hirsute | Not affected |
| 20.10 groovy | Not affected |
| 20.04 LTS focal | Not affected |
| 19.10 eoan | Not affected |
| 19.04 disco | Not affected |
| 18.10 cosmic | Not affected |
| 18.04 LTS bionic | Fixed 0.8.4-1+deb9u2build0.18.04.1 |
| 16.04 LTS xenial | Fixed 0.8.4-1ubuntu0.16.04.1~esm2  Ubuntu Pro |
| 14.04 LTS trusty | Fixed 0.7.5-1ubuntu2+esm2  Ubuntu Pro |

---

* [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-2018-20721?format=md#patch-details)

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### 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 |
| --- | --- |
| uriparser | * Upstream:   [cef2502](https://github.com/uriparser/uriparser/commit/cef25028de5ff872c2e1f0a6c562eb3ea9ecbce4.patch) |

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

9.8 · Critical

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | 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 | 9.8 · Critical |
  | Exploitability score | - |
  | Impact score | - |

**Vector:** CVSS:3.1/AV:N/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-2018-20721)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2018-20721)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2018-20721)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2018-20721)

### Related Ubuntu Security Notices (USN)

+ [USN-5172-1](https://usn.ubuntu.com/USN-5172-1)
+ uriparser vulnerabilities
+ 6 December 2021

+ [USN-5172-2](https://usn.ubuntu.com/USN-5172-2)
+ uriparser vulnerability
+ 9 December 2021

### Other references

* <https://github.com/uriparser/uriparser/commit/cef25028de5ff872c2e1f0a6c562eb3ea9ecbce4>
* <https://github.com/uriparser/uriparser/blob/master/ChangeLog>
* <https://www.cve.org/CVERecord?id=CVE-2018-20721>