---
title: "CVE-2020-5249\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-2020-5249?format=md
keywords: index, follow
---

# CVE-2020-5249

Publication date 2 March 2020

Last updated 25 August 2025

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**6.5 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2020-5249?format=md#impact-score)

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## Description

In Puma (RubyGem) before 4.3.3 and 3.12.4, if an application using Puma
allows untrusted input in an early-hints header, an attacker can use a
carriage return character to end the header and inject malicious content,
such as additional headers or an entirely new response body. This
vulnerability is known as HTTP Response Splitting. While not an attack in
itself, response splitting is a vector for several other attacks, such as
cross-site scripting (XSS). This is related to CVE-2020-5247, which fixed
this vulnerability but only for regular responses. This has been fixed in
4.3.3 and 3.12.4.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| puma | 20.04 LTS focal | Not affected |
| 19.10 eoan | Ignored end of life |
| 18.04 LTS bionic | Not in release |
| 16.04 LTS xenial | Not in release |
| 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**

6.5 · Medium

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 6.5 · Medium |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-5249)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2020-5249)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2020-5249)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2020-5249)

### Other references

* <https://github.com/puma/puma/security/advisories/GHSA-33vf-4xgg-9r58>
* <https://github.com/puma/puma/commit/c22712fc93284a45a93f9ad7023888f3a65524f3>
* <https://github.com/puma/puma/security/advisories/GHSA-84j7-475p-hp8v>
* <https://owasp.org/www-community/attacks/HTTP_Response_Splitting>
* <https://www.cve.org/CVERecord?id=CVE-2020-5249>