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Description

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.

PUBLISHED Reserved 2026-05-18 | Published 2026-06-19 | Updated 2026-06-19 | Assigner GitHub_M




LOW: 2.9CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P

Problem types

CWE-178: Improper Handling of Case Sensitivity

CWE-307: Improper Restriction of Excessive Authentication Attempts

Product status

>= 4.38.0, < 4.39.20
affected

References

github.com/...thelia/security/advisories/GHSA-hjj4-hfjm-fmrj

github.com/...ommit/b8985b57b70acdff8f204ed426ff619e763461ad

cve.org (CVE-2026-47203)

nvd.nist.gov (CVE-2026-47203)

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