CVE-2018-20028: Contao Information Disclosure via Access Control Flaws

contao/contao Updated 02 Oct 2025

Summary

13/05/2022

Disclosed on

CVE-2018-20028

CVE

Yes i

Fix available

Moderate

Severity

6.5

CVSS Score

CVE-2018-20028: Contao Information Disclosure via Access Control Flaws. Affects contao/contao across 3 version ranges.

>= 3.0.0, < 3.5.37 >= 4.4.0, < 4.4.31 >= 4.6.0, < 4.6.11

Fixed in 3.5.37, 4.4.31 or 4.6.11, depending on the release line you run. How to fix ↓

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Background

Contao is an open-source content management system (CMS) that allows users to create and manage websites. It provides a range of features, including a user-friendly interface, customizable templates, and a powerful backend. Contao is widely used by developers and website administrators to build and maintain websites of various sizes and complexities. However, versions 3.x before 3.5.37, 4.4.x before 4.4.31, and 4.6.x before 4.6.11 of Contao are vulnerable to an information disclosure issue due to incorrect access control.

Vulnerability Detail

The vulnerability in Contao allows unauthorized users to gain access to sensitive information by bypassing access controls. This can lead to the exposure of confidential data, such as user credentials, personal information, or other sensitive data stored within the CMS. The vulnerability is considered moderate in severity with a CVSS score of 6.5. It can be exploited remotely without any authentication, making it a potential target for attackers.

How To Fix

Fixed versions by release line

The minimum fixed version depends on the release line you run.

>= 3.0.0, < 3.5.37 3.5.37
```
composer require contao/contao:3.5.37
```
>= 4.4.0, < 4.4.31 4.4.31
```
composer require contao/contao:4.4.31
```
>= 4.6.0, < 4.6.11 4.6.11
```
composer require contao/contao:4.6.11
```

Tip — Not sure which release line you're on? Vulert can find the fix for the version you are using. Scan free →

Workaround

As a temporary workaround, users can implement additional access control measures at the server level to restrict unauthorized access to sensitive files and directories. This can be achieved by configuring the web server to deny access to specific URLs or by implementing authentication mechanisms, such as password protection or IP whitelisting, for accessing sensitive areas of the website.

Conclusion

The information disclosure vulnerability in Contao can have serious consequences, including data breaches and privacy violations. It is crucial for users to update their Contao installations to the latest patched versions to mitigate the risk. Additionally, implementing additional access control measures at the server level can provide an extra layer of security. For further support and assistance in vulnerability remediation, please contact DevNack.com.

See every vulnerability recorded for contao/contao →