Lack Of forward Secrecy

Lack of Forward Secrecy

Overview of the Vulnerability

Forward secrecy uses temporary keys for the exchange of information between two parties. If a server's private key is compromised the session is still secure as it uses ephemeral keys for the exchange. When the application lacks forward secrecy, these security guarantees will rely solely on a public and private key interaction. An attacker will only require a private key to decrypt the data in transit.

Business Impact

Lack of forward secrecy can lead to reputational damage for the business due to a loss in confidence and trust by users who identify that there isn’t any forward secrecy.

Steps to Reproduce

  1. Run a tool such as SSLScan, TestSLL, or SSLyze to scan the SSL/TLS configuration

  2. Observe the results showing the lack of forward secrecy:

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Proof of Concept (PoC)

The screenshot below demonstrates the use of a cipher suite with lack of forward secrecy:

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Recommendation(s)

It is recommended that only strong cipher suites are supported. As a guideline, the following cipher suites are recommended:

  • Ciphers such as ECDHE and DHE, which use perfect forward secrecy key exchange

  • Ciphers that use SHA256

  • AES-GCM is preferred for authentication ciphers. These are only available when TLS1.2 and TLS1.3 are in use

For more information, please see:

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