CVE-2026-47203 Vulnerability Analysis & Exploit Details

CVE-2026-47203 Vulnerability Summary

CVE-2026-47203: 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.

CVE-2026-47203 References

External References

• https://github.com/authelia/authelia/commit/b8985b57b70acdff8f204ed426ff619e763461ad
• https://github.com/authelia/authelia/security/advisories/GHSA-hjj4-hfjm-fmrj

CWE Common Weakness Enumeration

CAPEC Common Attack Pattern Enumeration and Classification

• Dictionary-based Password Attack CAPEC-16 An attacker tries each of the words in a dictionary as passwords to gain access to the system via some user's account. If the password chosen by the user was a word within the dictionary, this attack will be successful (in the absence of other mitigations). This is a specific instance of the password brute forcing attack pattern. Dictionary Attacks differ from similar attacks such as Password Spraying (CAPEC-565) and Credential Stuffing (CAPEC-600), since they leverage unknown username/password combinations and don't care about inducing account lockouts.
• Password Brute Forcing CAPEC-49 An adversary tries every possible value for a password until they succeed. A brute force attack, if feasible computationally, will always be successful because it will essentially go through all possible passwords given the alphabet used (lower case letters, upper case letters, numbers, symbols, etc.) and the maximum length of the password.
• Use of Known Domain Credentials CAPEC-560 An adversary guesses or obtains (i.e. steals or purchases) legitimate credentials (e.g. userID/password) to achieve authentication and to perform authorized actions under the guise of an authenticated user or service.
• Password Spraying CAPEC-565 In a Password Spraying attack, an adversary tries a small list (e.g. 3-5) of common or expected passwords, often matching the target's complexity policy, against a known list of user accounts to gain valid credentials. The adversary tries a particular password for each user account, before moving onto the next password in the list. This approach assists the adversary in remaining undetected by avoiding rapid or frequent account lockouts. The adversary may then reattempt the process with additional passwords, once enough time has passed to prevent inducing a lockout.
• Credential Stuffing CAPEC-600 An adversary tries known username/password combinations against different systems, applications, or services to gain additional authenticated access. Credential Stuffing attacks rely upon the fact that many users leverage the same username/password combination for multiple systems, applications, and services.
• Use of Known Kerberos Credentials CAPEC-652 An adversary obtains (i.e. steals or purchases) legitimate Kerberos credentials (e.g. Kerberos service account userID/password or Kerberos Tickets) with the goal of achieving authenticated access to additional systems, applications, or services within the domain.
• Use of Known Operating System Credentials CAPEC-653 An adversary guesses or obtains (i.e. steals or purchases) legitimate operating system credentials (e.g. userID/password) to achieve authentication and to perform authorized actions on the system, under the guise of an authenticated user or service. This applies to any Operating System.

Other 5 Recently Published CVEs Vulnerabilities

• CVE-2026-56082 – Capgo (Cap-go/capgo) before 12.128.2 contains an improper access control vulnerability in the SECURITY DEFINER PostgREST RPC function public.record...
• CVE-2026-56081 – Cap-go before 12.128.2 contains an authentication logic flaw that lets an attacker register and control an account bound to a victim's email addres...
• CVE-2026-56080 – Capgo before 12.128.2 contains a flaw in the Enforce Password Policy feature: after a Super Admin enables the policy and successfully changes their...
• CVE-2026-56079 – Capgo before 12.128.2 contains a cross-tenant authorization bypass vulnerability in PostgREST endpoints that allows org-scoped read API keys to acc...
• CVE-2026-56073 – Cap-go before 12.128.2 contains an authentication bypass vulnerability in OTP verification that allows attackers to bypass email verification by mo...