With 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.
An 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.
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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Vendor Solution
Upgrade to Lemonldap-NG-Portal 2.23.4 or later.
Vendor Workaround
For deployments that cannot upgrade to 2.23.4, set RequirePKCE to 1 on public Relying Parties so that a code challenge is always required. Relying Parties created through dynamic registration are always in "PKCE or secret" mode, so that endpoint has to be disabled as well.
Tracking
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Fri, 25 Sep 2026 01:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. With 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. An 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. | |
| Title | 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 | |
| Weaknesses | CWE-1390 | |
| References |
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Subscriptions
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MITRE
Status: PUBLISHED
Assigner: CPANSec
Published:
Updated: 2026-09-25T02:10:01.838Z
Reserved: 2026-09-15T23:43:48.309Z
Link: CVE-2026-92289
Vulnrichment
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NVD
Status : Received
Published: 2026-09-25T01:16:48.943
Modified: 2026-09-25T01:16:48.943
Link: CVE-2026-92289
Redhat
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OpenCVE Enrichment
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CWE-1390
Weak Authentication