CVE-2026-92289

9.1 CRITICAL

Published 2026-09-25 · Updated 2026-09-26

AI risk analysis

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.
Detection: No reliable host or network indicator is derivable from the published description.
Prioritized remediation: Upgrade to Lemonldap::NG::Portal version 2.23.4 or later.

auth-bypasswebperloidc

Analysis generated locally by qwen2.5:7b-instruct (no data left the box). AI-assisted — verify against primary sources before acting.

NVD 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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Weaknesses

CWE-1390

All references

Source data: NVD (nvd.nist.gov), public domain. Exploit-DB.ai adds local AI analysis for defensive use only.

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