#VU69935 Improper Verification of Cryptographic Signature in pac4j - CVE-2021-44878

Vulnerability identifier: #VU69935

Vulnerability risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-44878

CWE-ID: CWE-347

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
pac4j
Universal components / Libraries / Libraries used by multiple products

Vendor: pac4j

Description

The vulnerability allows a remote attacker to compromise the target system.

The vulnerability exists if an OpenID Connect provider supports the "none" algorithm, then pac4j does not refuse it without an explicit configuration on its side or for the "idtoken" response type. A remote attacker can 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.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

pac4j: before 5.3.1

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External links
https://github.com/pac4j/pac4j/commit/22b82ffd702a132d9f09da60362fc6264fc281ae
https://openid.net/specs/openid-connect-core-1_0.html#IDToken
https://www.pac4j.org/blog/cve_2021_44878_is_this_serious.html

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.