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Authelia allows open redirects on the logout endpoint

Moderate
clems4ever published GHSA-36f2-fcrx-fp4j Apr 21, 2021

Package

web (Authelia)

Affected versions

<4.27.4

Patched versions

>4.28.0

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

f0cb75e fix(handlers): logout redirection validation (#1908) v4.28.0

Workarounds

Using a reverse proxy to strip the query parameter from the affected endpoint.

References

#1908

CWE-601

Authelia v4.28.0

For more information

If you have any questions or comments about this advisory, please contact us. 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.

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CVE ID

CVE-2021-29456

Weaknesses

Credits