CVE-2020-26939: Medium severity bouncycastle Legion-of-the-bouncy-castle vulnerability

In Legion of the Bouncy Castle BC before 1.61 and BC-FJA before 1.0.1.2, attackers can obtain sensitive information about a private exponent because of Observable Differences in Behavior to Error Inputs. This occurs in org.bouncycastle.crypto.encodings.OAEPEncoding. Sending invalid ciphertext that decrypts to a short payload in the OAEP Decoder could result in the throwing of an early exception, potentially leaking some information about the private exponent of the RSA private key performing the encryption.

Legion of the Bouncy Castle BC and Legion of the Bouncy Castle BC-FJA could allow a remote attacker to obtain sensitive information, caused by observable differences in behavior to rrror inputs in org.bouncycastle.crypto.encodings.OAEPEncoding. By using the OAEP Decoder to send invalid ciphertext that decrypts to a short payload, a remote attacker could exploit this vulnerability to obtain sensitive information and use this information to launch further attacks against the affected system.