CVE-2021-29456

Description

### Impact Utilizing a HTTP query parameter an attacker is able to redirect users from the web application to any domain. The URL of the intended redirect should always be checked for safety prior to forwarding the user. Other endpoints of the web application already do this, they check both that the domain is using the HTTPS protocol and that it exists on a domain associated with the application. An attacker is able to use this unintended functionality to redirect users to malicious sites. This particular security issue allows the attacker to make a phishing attempt seem much more trustworthy to a user of the web application as the initial site before redirection is familiar to them, as well as the actual URL which they have theoretically visited frequently. While this security issue does not directly impact the security of the web application, it is still not an acceptable scenario for the reasons mentioned above. ### Patches f0cb75e1e102f95f91e9254c66c797e821857690 fix(handlers): logout redirection validation (#1908) [v4.28.0](https://github.com/authelia/authelia/releases/tag/v4.28.0) ### Workarounds Using a reverse proxy to strip the query parameter from the affected endpoint. ### References https://github.com/authelia/authelia/pull/1908 [CWE-601](https://cwe.mitre.org/data/definitions/601.html) [Authelia v4.28.0](https://github.com/authelia/authelia/tree/v4.28.0) ### For more information If you have any questions or comments about this advisory, please [contact us](https://github.com/authelia/authelia#contact-options). You may also contact us to request creating a back-ported fix for this if you are able to explain why you cannot upgrade; however upgrading is highly preferable.

How to fix CVE-2021-29456

To remediate CVE-2021-29456, upgrade the affected package to a fixed version below.

• —upgrade to 4.28.0 or later

Is CVE-2021-29456 being exploited?

Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.

Affected packages (1)