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Vulnerability record · CVE-2021-44878 · published 6 January 2022

CVE-2021-44878: Pac4j improper verification of cryptographic signature vulnerability

Pac4j · Pac4j

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.

7.5 CVSS 3.1 High EPSS 0.90% · top 42.1% CWE-347 · Improper verification of cryptographic signature
7.5CVSS 3.1 base score, v2 5.0
0.90%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/pac4j/pac4j/commit/22b82ffd702a132d9f09da60362fc6264fc281ae PatchThird Party Advisory
https://openid.net/specs/openid-connect-core-1_0.html#IDToken ProductThird Party Advisory
https://www.pac4j.org/blog/cve_2021_44878_is_this_serious.html MitigationVendor Advisory
https://github.com/pac4j/pac4j/commit/22b82ffd702a132d9f09da60362fc6264fc281ae PatchThird Party Advisory
https://openid.net/specs/openid-connect-core-1_0.html#IDToken ProductThird Party Advisory
https://www.pac4j.org/blog/cve_2021_44878_is_this_serious.html MitigationVendor Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-44878), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.