---
title: "CVE-2020-7663\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-2020-7663?format=md
keywords: index, follow
---

# CVE-2020-7663

Publication date 2 June 2020

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-2020-7663?format=md#impact-score)

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## Description

websocket-extensions ruby module prior to 0.1.5 allows Denial of Service
(DoS) via Regex Backtracking. The extension parser may take quadratic time
when parsing a header containing an unclosed string parameter value whose
content is a repeating two-byte sequence of a backslash and some other
character. This could be abused by an attacker to conduct Regex Denial Of
Service (ReDoS) on a single-threaded server by providing a malicious
payload with the Sec-WebSocket-Extensions header.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| ruby-websocket-extensions | 22.04 LTS jammy | Not affected |
| 21.10 impish | Not affected |
| 21.04 hirsute | Not affected |
| 20.10 groovy | Ignored end of life |
| 20.04 LTS focal | Fixed 0.1.2-1+deb9u1build0.20.04.1 |
| 19.10 eoan | Ignored end of life |
| 18.04 LTS bionic | Fixed 0.1.2-1+deb9u1build0.18.04.1 |
| 16.04 LTS xenial | Fixed 0.1.2-1+deb9u1build0.16.04.1 |
| 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)

## 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 | None |
  | Availability impact | High |
* Scores

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

**Vector:** CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-7663)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2020-7663)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2020-7663)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2020-7663)

### Related Ubuntu Security Notices (USN)

+ [USN-4502-1](https://usn.ubuntu.com/USN-4502-1)
+ websocket-extensions vulnerability
+ 16 September 2020

### Other references

* <https://blog.jcoglan.com/2020/06/02/redos-vulnerability-in-websocket-extensions>
* <https://github.com/faye/websocket-extensions-ruby/commit/aa156a439da681361ed6f53f1a8131892418838b>
* <https://github.com/faye/websocket-extensions-ruby/security/advisories/GHSA-g6wq-qcwm-j5g2>
* <https://snyk.io/vuln/SNYK-RUBY-WEBSOCKETEXTENSIONS-570830>
* <https://www.cve.org/CVERecord?id=CVE-2020-7663>