Pac4j token validation bypass if OpenID Connect provider supports none algorithm
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.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | org.pac4j:pac4j-oidc | < 4.5.5, >= 5.0, < 5.3.1 | 4.5.5, 5.3.1 |
References
- https://nvd.nist.gov/vuln/detail/CVE-2021-44878
- https://github.com/pac4j/pac4j/commit/09684e0de1c4753d22c53b8135d4ef61cfda76f7
- https://github.com/pac4j/pac4j/commit/22b82ffd702a132d9f09da60362fc6264fc281ae
- https://github.com/pac4j/pac4j/commit/9c87bbc536ed5d05f940ae015403120df2935589
- https://github.com/pac4j/pac4j
- https://openid.net/specs/openid-connect-core-1_0.html#IDToken
- https://www.pac4j.org/4.5.x/docs/release-notes.html
- https://www.pac4j.org/blog/cve_2021_44878_is_this_serious.html
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N- Weakness (CWE)
CWE-347- Platform
- Java / Kotlin (Maven)
- Package
org.pac4j:pac4j-oidc- Disclosed
- 08.01.2022
- Updated
- 11.10.2026 11:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-xhw6-hjc9-679m - CC BY 4.0
Vulnerability history: org.pac4j:pac4j-oidc
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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