1. Vulnerability Description

• When performing secure communication, insufficient renegotiation restrictions may allow an attacker to cause DoS attacks.

2. How to check vulnerability

• You can check this vulnerability using the OpenSSL binary.

$ openssl s_client -connect www.example.com:443

• If you enter the above command — appears and you see it’s paused, and you can try to renegotiate it by entering the upper case R.
• At that time, if an error occurs and no action occurs, it is not vulnerable.
• If RENEGOTIATING is successful, there has the vulnerability. )

3. Vulnerability Countermeasure

• It is recommended to upgrade to the latest OpenSSL version.
  • (Recommend OpenSSL version 0.9.8m or higher.)