An error in the Bouncy Castle BC-JAVA PKIX CompositeVerifier allows it to consider an empty signature sequence valid. This flaw is classified as CWE‑327, a broken or risky cryptographic algorithm. It is inferred that an attacker can construct a certificate chain with an empty signature sequence that the vulnerable verifier will accept, effectively allowing the forging of trusted certificates.

The issue impacts Bouncy Castle Inc.’s BC-JAVA library from version 1.49 up to and including 1.83. All Java applications that depend on the bc‑pkix module in these releases are vulnerable until an upgraded version is installed.

The vulnerability has a CVSS score of 6.3. The EPSS score indicates a very low but nonzero exploitation probability, and the vulnerability is not listed in CISA’s KEV catalog. The likely attack vector is through the construction of a forged certificate chain. Any application that performs PKIX verification using the affected library could be compromised. Without an available exploit track, the risk remains significant because the flaw enables the attacker to bypass certificate validation entirely, granting them authority equivalent to a trusted party.