An integer underflow flaw, leading to a buffer overflow, was found in the way OpenSSL decoded malformed Base64-encoded inputs. An attacker able to make an application using OpenSSL decode a specially crafted Base64-encoded input (such as a PEM file) could use this flaw to cause the application to crash. Note: this flaw is not exploitable via the TLS/SSL protocol because the data being transferred is not Base64-encoded.