iSEC Partners Releases SSLyze

Transport Layer Security (TLS), commonly called SSL, is one of the most widely used protocols to secure network communications. As costs fall and user security and privacy expectations rise companies are deploying it more widely every year. Attacks against the CA system, SSL implementation flaws and aging protocol versions have grabbed news headlines, bringing attention to weak configurations, and the need to avoid them. Additionally, server misconfigurations have always greatly increased the overhead caused by SSL, slowing the transition to improved communications security.

To help improve system configurations, iSEC is releasing the free software “SSLyze” tool. We have found this tool helpful for analyzing the configuration of SSL servers and for identifying misconfigurations such as the use of outdated protocol versions, weak hash algorithms in trust chains, insecure renegotiation, and session resumption settings.

SSLyze is a stand-alone python application that looks for classic SSL misconfigurations, while providing the advanced user with the opportunity to customize the application via a simple plugin interface. Right now it supports the following features:

  • Insecure renegotiation testing
  • Scanning for weak strength ciphers
  • Checking for SSLv2, SSLv3 and TLSv1 versions
  • Server certificate information dump and basic validation
  • Session resumption capabilities and actual resumption rate measurement
  • Support for client certificate authentication
  • Simultaneous scanning of multiple servers, versions and ciphers

For example, SSLyze can help user’s identify server configurations vulnerable to THC’s recently released SSL DOS attack ( by checking the server’s support for client-initiated renegotiations. For more information on testing for client-initiated renegotiations, see:

The project is hosted on Git at the following URL:

Thanks and we hope our tool helps you quickly discover SSL issues in your environment!

  • Alban Diquet
  • Aaron Grattafiori

Note: for questions or comments about the tool, please

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