---
title: "CVE-2020-5255\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-2020-5255?format=md
keywords: index, follow
---

# CVE-2020-5255

Publication date 30 March 2020

Last updated 25 August 2025

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**4.3 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2020-5255?format=md#impact-score)

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## Description

In Symfony before versions 4.4.7 and 5.0.7, when a `Response` does not
contain a `Content-Type` header, affected versions of Symfony can fallback
to the format defined in the `Accept` header of the request, leading to a
possible mismatch between the response's content and `Content-Type`
header. When the response is cached, this can prevent the use of the
website by other users. This has been patched in versions 4.4.7 and 5.0.7.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| symfony | 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 | Ignored end of life |
| 18.04 LTS bionic | Not affected |
| 16.04 LTS xenial | Not affected |
| 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)
* [Patch details](https://ubuntu.com/security/CVE-2020-5255?format=md#patch-details)

### 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 |
| --- | --- |
| symfony | * Upstream:   [dca3434](https://github.com/symfony/symfony/commit/dca343442e6a954f96a2609e7b4e9c21ed6d74e6) |

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

4.3 · Medium

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 4.3 · Medium |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-5255)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2020-5255)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2020-5255)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2020-5255)

### Other references

* <https://symfony.com/blog/cve-2020-5255-prevent-cache-poisoning-via-a-response-content-type-header>
* <https://github.com/symfony/symfony/commit/dca343442e6a954f96a2609e7b4e9c21ed6d74e6>
* <https://github.com/symfony/symfony/security/advisories/GHSA-mcx4-f5f5-4859>
* <https://www.cve.org/CVERecord?id=CVE-2020-5255>