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Vulnerability · Published Sep 25, 2026 · Assigned by CPANSec

CVE-2026-92288Lemonldap::NG::Portal versions from 2.20.0 before 2.21.6, from 2.22.0 before 2.23.4 for Perl allow unauthenticated OAuth2 token introspection because checkEndPointAuthenticationCredentials does not verify the client secret of a public Relying Party

Critical 9.1

In plain English

A critical-severity security flaw in Lemonldap-NG-Portal. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 39% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.1Critical
Exploit odds (30 days)0.4%top 61.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official description

Lemonldap::NG::Portal versions from 2.20.0 before 2.21.6, from 2.22.0 before 2.23.4 for Perl allow unauthenticated OAuth2 token introspection because checkEndPointAuthenticationCredentials does not verify the client secret of a public Relying Party. checkEndPointAuthenticationCredentials() skips the secret comparison for a Relying Party marked public and still returns the authentication method deduced from the request, client_secret_basic or client_secret_post. introspection() rejects a caller only when that method is missing or none, so a request carrying a public client_id and an arbitrary or empty secret passes the endpoint's authentication check. An attacker who holds an access token and knows the client_id of any public Relying Party can confirm the token is active and read its metadata, including scope, audience, expiry and the sub claim. The sub claim is computed with the calling Relying Party's user identifier attribute, so an attacker can translate a user identifier from one Relying Party to another, defeating per-client and pseudonymous identifiers.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:13lemonldap-ng2.21.2+ds-1+deb13u4DEBIAN-CVE-2026-92288
Debian:14lemonldap-ng2.23.4+ds-1DEBIAN-CVE-2026-92288
Ubuntu:22.04:LTSlemonldap-ngno fix listedUBUNTU-CVE-2026-92288
Ubuntu:24.04:LTSlemonldap-ngno fix listedUBUNTU-CVE-2026-92288
Ubuntu:26.04:LTSlemonldap-ngno fix listedUBUNTU-CVE-2026-92288
Ubuntu:26.10lemonldap-ngno fix listedUBUNTU-CVE-2026-92288

Affected products (as reported)

VendorProductVersions
Lemonldap-NG-Portal 2.20.0 – before 2.21.62.22.0 – before 2.23.4

Weakness: CWE-1390 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References