CVE-2021-44878 Pac4j token validation bypass if OpenID Connect provider supports none algorithm

What is CVE-2021-44878?

CVE-2021-44878 is a high-severity authentication bypass vulnerability in n/a, published on 6 Jan 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

If an OpenID Connect provider supports the "none" algorithm (i.e., tokens with no signature), pac4j v5.3.0 (and prior) does not refuse it without an explicit configuration on its side or for the "idtoken" response type which is not secure and violates the OpenID Core Specification. The "none" algorithm does not require any signature verification when validating the ID tokens, which allows the attacker to bypass the token validation by injecting a malformed ID token using "none" as the value of "alg" key in the header with an empty signature value.

Weakness: CWE-347

Which versions are affected by CVE-2021-44878?

4 open source packages ship an affected version, including org.pac4j:pac4j-oidc. It affects 1 product.

Products include Pac4j Pac4j.

How do I fix CVE-2021-44878?

Upgrade org.pac4j:pac4j-oidc to a fixed version for your release line: 4.5.5 or 5.3.1.

Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.

Is CVE-2021-44878 being exploited?

There is no known exploitation of CVE-2021-44878 in the wild and no public exploit code.

Other vulnerabilities in n/a

• CVE-2026-40459 LDAP Injection in PAC4J High 8.7
• CVE-2026-40458 Cross-Site Request Forgery in PAC4J High 7.0
• CVE-2019-10755 Use of Cryptographically Weak Pseudo-Random Number Generator in org.pac4j:pac4j-saml Medium 4.9

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-xhw6-hjc9-679m.