CVE-2023-36820

io.micronaut.security:micronaut-security-oauth2 has invalid IdTokenClaimsValidator logic on aud

                return issuer.equalsIgnoreCase(iss) &&
                        audiences.contains(clientId) &&
                                validateAzp(claims, clientId, audiences);

package cve;

import io.micronaut.context.annotation.Replaces;
import io.micronaut.context.annotation.Requires;
import io.micronaut.core.annotation.NonNull;
import io.micronaut.core.util.StringUtils;
import io.micronaut.security.config.SecurityConfigurationProperties;
import io.micronaut.security.oauth2.client.IdTokenClaimsValidator;
import io.micronaut.security.oauth2.configuration.OauthClientConfiguration;
import io.micronaut.security.oauth2.configuration.OpenIdClientConfiguration;
import io.micronaut.security.token.jwt.generator.claims.JwtClaims;
import io.micronaut.security.token.jwt.validator.JwtClaimsValidatorConfigurationProperties;

import javax.inject.Singleton;
import java.net.URL;
import java.util.Collection;
import java.util.List;
import java.util.Optional;

@Requires(property = SecurityConfigurationProperties.PREFIX + ".authentication", value = "idtoken")
@Requires(property = JwtClaimsValidatorConfigurationProperties.PREFIX + ".openid-idtoken", notEquals = StringUtils.FALSE)
@Singleton
@Replaces(IdTokenClaimsValidator.class)
public class IdTokenClaimsValidatorReplacement extends IdTokenClaimsValidator {
    public IdTokenClaimsValidatorReplacement(Collection<OauthClientConfiguration> oauthClientConfigurations) {
        super(oauthClientConfigurations);
    }

    @Override
    protected boolean validateIssuerAudienceAndAzp(@NonNull JwtClaims claims,
                                                   @NonNull String iss,
                                                   @NonNull List<String> audiences,
                                                   @NonNull String clientId,
                                                   @NonNull OpenIdClientConfiguration openIdClientConfiguration) {
        if (openIdClientConfiguration.getIssuer().isPresent()) {
            Optional<URL> issuerOptional = openIdClientConfiguration.getIssuer();
            if (issuerOptional.isPresent()) {
                String issuer = issuerOptional.get().toString();
                return issuer.equalsIgnoreCase(iss) &&
                        audiences.contains(clientId) &&
                                validateAzp(claims, clientId, audiences);
            }
        }
        return false;
    }
}
``

Any OIDC setup using Micronaut where multiple OIDC applications exists for the same issuer but token auth are not meant to be shared.

CVE-2023-36820 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.11.1, 3.10.2, 3.9.6, 3.8.4, 3.7.4, 3.6.6, 3.5.3, 3.4.3, 3.3.2, 3.2.4, 3.1.2); upgrading removes the vulnerable code path.

Kodem intelligence

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1. What is CVE-2023-36820? CVE-2023-36820 is a medium-severity security vulnerability in io.micronaut.security:micronaut-security-oauth2 (maven), affecting versions >= 3.11.0, < 3.11.1. It is fixed in 3.11.1, 3.10.2, 3.9.6, 3.8.4, 3.7.4, 3.6.6, 3.5.3, 3.4.3, 3.3.2, 3.2.4, 3.1.2.
2. How severe is CVE-2023-36820? CVE-2023-36820 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of io.micronaut.security:micronaut-security-oauth2 are affected by CVE-2023-36820? io.micronaut.security:micronaut-security-oauth2 (maven) versions >= 3.11.0, < 3.11.1 is affected.
4. Is there a fix for CVE-2023-36820? Yes. CVE-2023-36820 is fixed in 3.11.1, 3.10.2, 3.9.6, 3.8.4, 3.7.4, 3.6.6, 3.5.3, 3.4.3, 3.3.2, 3.2.4, 3.1.2. Upgrade to this version or later.
5. Is CVE-2023-36820 exploitable, and should I be worried? Whether CVE-2023-36820 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-36820 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-36820?
   • Upgrade io.micronaut.security:micronaut-security-oauth2 to 3.11.1 or later
   • Upgrade io.micronaut.security:micronaut-security-oauth2 to 3.10.2 or later
   • Upgrade io.micronaut.security:micronaut-security-oauth2 to 3.9.6 or later
   • Upgrade io.micronaut.security:micronaut-security-oauth2 to 3.8.4 or later
   • Upgrade io.micronaut.security:micronaut-security-oauth2 to 3.7.4 or later
   • Upgrade io.micronaut.security:micronaut-security-oauth2 to 3.6.6 or later
   • Upgrade io.micronaut.security:micronaut-security-oauth2 to 3.5.3 or later
   • Upgrade io.micronaut.security:micronaut-security-oauth2 to 3.4.3 or later
   • Upgrade io.micronaut.security:micronaut-security-oauth2 to 3.3.2 or later
   • Upgrade io.micronaut.security:micronaut-security-oauth2 to 3.2.4 or later
   • Upgrade io.micronaut.security:micronaut-security-oauth2 to 3.1.2 or later