CVE-2021-32637 Authentication bypassed with malformed request URI

Critical 10.0 Published 28 May 2021 Updated 3 Aug 2024

Attackers can bypass authentication in Authelia when used with nginx by sending malformed HTTP requests, requiring an upgrade or configuration change.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2021-32637?

CVE-2021-32637 is a critical authentication bypass vulnerability in authelia, published on 28 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Authelia is a a single sign-on multi-factor portal for web apps. This affects uses who are using nginx ngx_http_auth_request_module with Authelia, it allows a malicious individual who crafts a malformed HTTP request to bypass the authentication mechanism. It additionally could theoretically affect other proxy servers, but all of the ones we officially support except nginx do not allow malformed URI paths. The problem is rectified entirely in v4.29.3. As this patch is relatively straightforward we can back port this to any version upon request. Alternatively we are supplying a git patch to 4.25.1 which should be relatively straightforward to apply to any version, the git patches for specific versions can be found in the references. The most relevant workaround is upgrading. You can also add a block which fails requests that contains a malformed URI in the internal location block.

Weakness: CWE-287

Which versions are affected by CVE-2021-32637?

2 open source packages ship an affected version, including github.com/authelia/authelia/v4. It affects 1 product.

Package	Affected	Fixed in
`github.com/authelia/authelia/v4` Go	From `4.0.0-alpha1`	`4.29.3`
`github.com/authelia/authelia/v4` Go	From `4.0.0-alpha1`	`4.29.3`

Products include Authelia Authelia.

How do I fix CVE-2021-32637?

Upgrade github.com/authelia/authelia/v4 to 4.29.3 or later.

Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.

Is CVE-2021-32637 being exploited?

There is no known exploitation of CVE-2021-32637 in the wild and no public exploit code.

Sources

Also known as GHSA-68wm-pfjf-wqp6.