The vulnerability specifically affects RSA CMS signatures without signed attributes. The core issue lies in how the signature verification process handles PKCS#1 v1.5 padding when signed attributes are missing. The 'doVerify' method in Bouncy Castle's CMS SignerInformation class is responsible for signature validation. When signed attributes are absent, the verification logic likely fails to properly validate the padding structure, allowing an attacker to exploit observable discrepancies (CWE-203) in error responses or timing to perform a Bleichenbacher attack. This aligns with the CWE-203 classification and the described attack vector.