{"id":"CVE-2026-92289","published":"2026-09-25T01:16:48.943","lastModified":"2026-09-26T23:16:38.897","description":"Lemonldap::NG::Portal versions from 2.23.0 before 2.23.4 for Perl allow a PKCE bypass for public Relying Parties in \"PKCE or secret\" mode because checkEndPointAuthenticationCredentials does not verify the client secret.\n\nWith oidcRPMetaDataOptionsRequirePKCE set to 2, the authorization endpoint issues a code even when the request carries no code_challenge, and token() admits the exchange as long as a challenge was stored or an authentication method was returned for the caller. checkEndPointAuthenticationCredentials() skips the secret comparison for a Relying Party marked public and still returns the method deduced from the request, so any Basic or form credential satisfies the secret branch. validatePKCEChallenge() then passes, because neither a challenge nor a verifier is present.\n\nAn attacker who intercepts an authorization code issued to a public Relying Party can exchange it for the user's access, ID and refresh tokens by replaying the client_id with an arbitrary secret, which is the attack PKCE prevents. Dynamic client registration creates every Relying Party in this mode.","cvssScore":9.1,"cvssSeverity":"CRITICAL","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","cwes":["CWE-1390"],"vendors":[],"products":[],"references":[{"url":"https://gitlab.ow2.org/lemonldap-ng/lemonldap-ng/-/releases/v2.23.4","tags":[]},{"url":"https://gitlab.ow2.org/lemonldap-ng/lemonldap-ng/-/work_items/3719","tags":[]},{"url":"http://www.openwall.com/lists/oss-security/2026/09/25/2","tags":[]},{"url":"https://gitlab.ow2.org/lemonldap-ng/lemonldap-ng/-/work_items/3719","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":{"summary":"The flaw allows an attacker to bypass PKCE validation for public Relying Parties, enabling them to obtain user tokens by replaying client_id with an arbitrary secret.","exploitability":"Exploitation is moderately hard as it requires intercepting an authorization code and replaying it with a fabricated secret, but preconditions include dynamic client registration in 'PKCE or secret' mode.","blast_radius":"If exploited, the attack could lead to unauthorized access to user accounts, as the attacker can obtain access, ID, and refresh tokens for the user.","remediation":"Upgrade to Lemonldap::NG::Portal version 2.23.4 or later.","detection":"No reliable host or network indicator is derivable from the published description.","tags":["auth-bypass","web","perl","oidc"],"model":"qwen2.5:7b-instruct","analyzedAt":"2026-09-28T08:52:54.199Z"}}