In the LDAP authenticator, an empty or null password is forwarded to ldap_bind(). Per RFC 4513 section 5.1.2, a bind request with a valid DN and an empty password constitutes an unauthenticated bind, which many LDAP directory servers accept as successful. An attacker who knows any valid user email address in the directory can therefore authenticate as that user without possessing a password. Additionally, non-string values (null, false, arrays) are either coerced to empty strings by ldap_bind(), raise TypeErrors, or are misinterpreted as find conditions in _findUser(), all of which can lead to unintended authentication outcomes.
In the LinOTP authenticator, the same missing guard allows non-string credentials to be concatenated into the LinOTP verification request, and in the mixed-authentication branch an empty password is accepted against a stored hash of the empty string.
A secondary issue in the LDAP authenticator is that newly created user accounts (auto-provisioned on first LDAP login) were assigned an empty password. Because the save path skips validation, the empty string is hashed and stored. If the user later ceases to be found in LDAP and the mixed-authentication fallback is used, the stored hash of the empty string verifies against an empty password, again permitting unauthenticated access.
The vulnerability requires that the affected plugin (LdapAuth or LinOTPAuth) is enabled on the MISP instance and that the attacker knows at least one valid email address registered in the directory or MISP user store. No prior authentication is required. Successful exploitation grants the attacker the full privileges of the impersonated user, which may include administrative access to threat intelligence data.
Version affected: ≤2.5.45
Analysis
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Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
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| MISP | MISP | affected |
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Vendor Solution
The fix adds explicit type and emptiness validation for the email and password fields in both LdapAuthenticate and LinOTPAuthenticate before any authentication logic is invoked. Non-string or empty credentials are rejected with a logged error and a false return. Additionally, the LDAP authenticator now assigns a cryptographically random password to auto-provisioned user accounts instead of an empty string, preventing the stored hash of '' from being verifiable in the mixed-authentication fallback path. The LinOTP authenticator also rejects an empty password specifically in the mixed-authentication branch where the password is checked against the local database.
Tracking
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| Link | Providers |
|---|---|
| https://github.com/MISP/MISP/commit/0ee058548 |
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Mon, 14 Sep 2026 13:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | The LdapAuth and LinOTPAuth authentication plugins in MISP contain an authentication bypass vulnerability. Both LdapAuthenticate and LinOTPAuthenticate replace CakePHP's FormAuthenticate class but fail to replicate its _checkFields() input validation guard. As a result, the email and password fields extracted from the login request are passed to downstream authentication logic without verifying that they are non-empty strings. In the LDAP authenticator, an empty or null password is forwarded to ldap_bind(). Per RFC 4513 section 5.1.2, a bind request with a valid DN and an empty password constitutes an unauthenticated bind, which many LDAP directory servers accept as successful. An attacker who knows any valid user email address in the directory can therefore authenticate as that user without possessing a password. Additionally, non-string values (null, false, arrays) are either coerced to empty strings by ldap_bind(), raise TypeErrors, or are misinterpreted as find conditions in _findUser(), all of which can lead to unintended authentication outcomes. In the LinOTP authenticator, the same missing guard allows non-string credentials to be concatenated into the LinOTP verification request, and in the mixed-authentication branch an empty password is accepted against a stored hash of the empty string. A secondary issue in the LDAP authenticator is that newly created user accounts (auto-provisioned on first LDAP login) were assigned an empty password. Because the save path skips validation, the empty string is hashed and stored. If the user later ceases to be found in LDAP and the mixed-authentication fallback is used, the stored hash of the empty string verifies against an empty password, again permitting unauthenticated access. The vulnerability requires that the affected plugin (LdapAuth or LinOTPAuth) is enabled on the MISP instance and that the attacker knows at least one valid email address registered in the directory or MISP user store. No prior authentication is required. Successful exploitation grants the attacker the full privileges of the impersonated user, which may include administrative access to threat intelligence data. Version affected: ≤2.5.45 | |
| Title | MISP LdapAuth and LinOTPAuth Authentication Bypass via Empty or Non-String Credentials | |
| Weaknesses | CWE-20 CWE-287 |
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cvssV4_0
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MITRE
Status: PUBLISHED
Assigner: CIRCL
Published:
Updated: 2026-09-14T13:55:49.225Z
Reserved: 2026-09-14T13:22:04.165Z
Link: CVE-2026-90961
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