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
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.
"}],"value":"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."}],"title":"MISP LdapAuth and LinOTPAuth Authentication Bypass via Empty or Non-String Credentials","x_gcve":[{"extensions":{"bcp-05-x-01":{"ai_annotations":[{"ai_level":"generated","description":"Draft vulnerability metadata was generated from a git-format patch using an Ollama-hosted language model. Human validation is required before publication.","gna_source":1,"models":[{"gna_source":1,"identifier":"qwen3.8:27b","name":"qwen3.8:27b","source":"ollama"}],"review_status":"review","scope":"record","tags":["ai-computer-assisted:llm-generated","ai-computer-assisted:classification"]}]},"bcp-05-x-02":{"x_patch2vuln":{"assumptions":["The LDAP directory server is configured to accept unauthenticated (empty-password) binds, which is common but not universal; if the directory rejects empty-password binds, the LDAP-specific bypass is mitigated at the directory level, though the non-string credential and empty-password-hash issues remain.","The attacker must know at least one valid email address that exists in the LDAP directory or MISP user store.","The LdapAuth or LinOTPAuth plugin is enabled on the affected MISP instance.","CVSS impact ratings assume the attacker can impersonate a user with high privileges (e.g., admin); actual impact scales with the privileges of the specific user impersonated.","The exact fixed version is not specified in the patch metadata; the fix commit is 238 commits after tag v2.5.46, suggesting the fix landed in a release after 2.5.46, but the precise version boundary is unconfirmed.","The LinOTP empty-password bypass in the mixed-auth branch requires the mixedauth setting to be enabled."],"commit":"0ee0585486cd2c9df49e4f14d48a32a953666e3a","confidence":"high","credits":[{"lang":"en","type":"reporter","value":"elhoim (David André)"},{"lang":"en","type":"remediation developer","value":"iglocska"},{"lang":"en","type":"remediation developer","value":"Claude Opus 5 (1M context)"}],"cvssRationale":"AV:N: The vulnerability is exploitable over the network via the MISP web login endpoint. AC:L: Exploitation requires only sending a login request with an empty or non-string password field; no race conditions, specific directory configuration beyond accepting unauthenticated binds (which is common), or other special conditions are needed. AT:N: No attack target manipulation is required. PR:N: No prior authentication is needed; the attacker is attempting to authenticate. UI:N: No user interaction is required. VC:H: Successful exploitation grants the attacker the full data-access privileges of the impersonated user, potentially including all MISP threat intelligence data. VI:H: The attacker can create, modify, or delete MISP objects, tags, and configurations at the privilege level of the impersonated user. VA:N: No direct availability impact is demonstrated. SC/SI/SA:N: No separate subsequent system is identified; the impact is contained to the MISP instance itself.","draft":false,"fixSummary":"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.","generatedAt":"2026-09-14T13:14:35.161935Z","generator":"patch2vuln.py","model":"qwen3.8:27b","modelComparison":{"rankings":[{"agreementScore":9,"assumptionCount":6,"confidence":"high","model":"qwen3.8:27b","score":5}],"selectedModel":"qwen3.8:27b","selectionMethod":"deterministic-consensus-v1","selectionNotice":"The selected result is closest to model consensus; this heuristic does not establish factual correctness and human review remains required."},"patchSha256":"01b60b396532e5f6ff5efca8c41961e701b7b6c539edcf49ad29aba06a906149","patchSummary":"In LdapAuthenticate.php: (1) email and password are now extracted with isset() defaults to empty string; (2) a guard clause checks is_string() and non-emptiness for both fields, logging an error and returning false on failure; (3) the auto-provisioned user creation block now calls $userModel->generateRandomPassword() and stores that value in both 'password' and 'confirm_password' fields instead of empty strings. In LinOTPAuthenticate.php: (1) email, password, and otp are extracted with isset() defaults; (2) a guard clause checks is_string() and non-emptiness for email and is_string() for password, logging and returning false on failure; (3) in the mixed-authentication branch, an additional check rejects an empty password before calling _findUser().","patchTruncated":false,"patches":[{"commit":"0ee0585486cd2c9df49e4f14d48a32a953666e3a","patchSha256":"01b60b396532e5f6ff5efca8c41961e701b7b6c539edcf49ad29aba06a906149","source":"https://github.com/MISP/MISP/commit/0ee058548.patch","sourceUrl":"https://github.com/MISP/MISP/commit/0ee058548.patch","subject":"fix: [security] Reject empty and non-string credentials in"}],"source":"https://github.com/MISP/MISP/commit/0ee058548.patch","subject":"fix: [security] Reject empty and non-string credentials in","tagVersionBoundary":{"commits_after_fix":238,"repository":"https://github.com/MISP/MISP","tag":"v2.5.46","version":"2.5.46","version_type":"semver"},"weaknessRationale":[{"cweId":"CWE-287","rationale":"The primary impact is an authentication bypass: empty or non-string credentials allow an unauthenticated attacker to be authenticated as a known directory user. The root cause is the absence of the credential validation guard that FormAuthenticate normally provides."},{"cweId":"CWE-20","rationale":"The underlying technical weakness is the failure to validate that user-supplied credential fields are non-empty strings before passing them to ldap_bind(), the LinOTP verifier, or _findUser(). Non-string types (null, false, arrays) and empty strings are all accepted and produce unintended authentication behavior."}]}}},"recordType":"advisory","vulnId":"GCVE-1-2026-20246"}]}},"cveMetadata":{"assignerOrgId":"5a6e4751-2f3f-4070-9419-94fb35b644e8","assignerShortName":"CIRCL","cveId":"CVE-2026-90961","datePublished":"2026-09-14T13:22:07.185Z","dateReserved":"2026-09-14T13:22:04.165Z","dateUpdated":"2026-09-14T13:55:49.225Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-14 14:17:21","lastModifiedDate":"2026-09-14 14:17:21","problem_types":["CWE-20","CWE-287","CWE-287 CWE-287 Improper Authentication","CWE-20 CWE-20 Improper Input Validation"],"metrics":{"cvssMetricV40":[{"source":"5a6e4751-2f3f-4070-9419-94fb35b644e8","type":"Secondary","cvssData":{"version":"4.0","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","baseScore":9.3,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH","vulnAvailabilityImpact":"LOW","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-09-14T13:55:28.674675Z","id":"CVE-2026-90961","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"90961","Ordinal":"1","Title":"MISP LdapAuth and LinOTPAuth Authentication Bypass via Empty or ","CVE":"CVE-2026-90961","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"90961","Ordinal":"1","NoteData":"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.\n\nIn 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.\n\nIn 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.\n\nA 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.\n\nThe 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.\n\n\nVersion affected: ≤2.5.45","Type":"Description","Title":"MISP LdapAuth and LinOTPAuth Authentication Bypass via Empty or "}]}}}