authelia up to 4.39.19 case sensitivity

Summaryinfo

A vulnerability identified as problematic has been detected in authelia up to 4.39.19. Affected by this vulnerability is an unknown functionality. This manipulation causes case sensitivity. This vulnerability appears as CVE-2026-47203. The attack may be initiated remotely. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in authelia up to 4.39.19. Affected by this vulnerability is some unknown functionality. The manipulation with an unknown input leads to a case sensitivity vulnerability. The CWE definition for the vulnerability is CWE-178. The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results. As an impact it is known to affect confidentiality. The summary by CVE is:

Authelia is an open-source authentication and authorization server providing two-factor authentication and single sign-on (SSO) for applications via a web portal. In versions 4.38.0 through 4.39.19, when a user authenticates via Basic Auth (i.e via the `Authorization` header with the `Basic` scheme) on the authz verification endpoint, Authelia takes the username directly from the `Authorization` header and passes it as is to the regulation system for ban checking and attempt recording. LDAP treats usernames case insensitively : `john`, `John`, and `JOHN` all bind as the same user. But the regulation SQL queries treat the lookup of these values in certain scenarios as case sensitive. This allows each variation of a usernames case to have its own ban bucket. Upgrade to 4.39.20 to receive a patch. As a workaround, explicitly disable the basic auth mechanism.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-47203 since 05/19/2026. The exploitation appears to be difficult. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available.

It is declared as proof-of-concept.

Upgrading to version 4.39.20 eliminates this vulnerability. Applying the patch b8985b57b70acdff8f204ed426ff619e763461ad is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-38082). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Name

• authelia

Version

• 4.39.0
• 4.39.1
• 4.39.2
• 4.39.3
• 4.39.4
• 4.39.5
• 4.39.6
• 4.39.7
• 4.39.8
• 4.39.9
• 4.39.10
• 4.39.11
• 4.39.12
• 4.39.13
• 4.39.14
• 4.39.15
• 4.39.16
• 4.39.17
• 4.39.18
• 4.39.19

License

• open-source

Website

• Product: https://github.com/authelia/authelia/

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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