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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-92289
StatePUBLISHED
AssignerCPANSec
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-25 01:16:48 UTC
Updated2026-09-25 03:16:58 UTC
DescriptionLemonldap::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.

Risk And Classification

Problem Types: CWE-1390 | CWE-1390 CWE-1390 Weak Authentication

References

ReferenceSourceLinkTags
gitlab.ow2.org/lemonldap-ng/lemonldap-ng/-/work_items/3719 9b29abf9-4ab0-4765-b253-1875cd9b441e gitlab.ow2.org
gitlab.ow2.org/lemonldap-ng/lemonldap-ng/-/releases/v2.23.4 9b29abf9-4ab0-4765-b253-1875cd9b441e gitlab.ow2.org
www.openwall.com/lists/oss-security/2026/09/25/2 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

Solutions

CNA: Upgrade to Lemonldap-NG-Portal 2.23.4 or later.

Workarounds

CNA: 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.

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