Free and open-source vulnerability scanner
Mageni eases for you the vulnerability scanning, assessment, and management process. It is free and open-source.
Install NowAvailable for macOS, Windows, and Linux
Diffie-Hellman Ephemeral Key Exchange DoS Vulnerability (SSL/TLS, D(HE)ater)
Information
Severity
Severity
Family
Family
CVSSv2 Base
CVSSv2 Base
CVSSv2 Vector
CVSSv2 Vector
Solution Type
Solution Type
Created
Created
Modified
Modified
Summary
The remote SSL/TLS server is supporting Diffie-Hellman ephemeral (DHE) Key Exchange algorithms and thus could be prone to a denial of service (DoS) vulnerability.
Insight
Insight
The Diffie-Hellman Key Agreement Protocol allows remote attackers (from the client side) to send arbitrary numbers that are actually not public keys, and trigger expensive server-side DHE modular-exponentiation calculations, aka a D(HE)ater attack. The client needs very little CPU resources and network bandwidth. The attack may be more disruptive in cases where a client can require a server to select its largest supported key size. The basic attack scenario is that the client must claim that it can only communicate with DHE, and the server must be configured to allow DHE.
Detection Method
Detection Method
Checks the supported cipher suites of the remote SSL/TLS server.
Solution
Solution
- DHE key exchange should be disabled if no other mitigation mechanism can be used and either elliptic-curve variant of Diffie-Hellman (ECDHE) or RSA key exchange is supported by the clients. The fact that RSA key exchange is not forward secret should be considered. - Limit the maximum number of concurrent connections in e.g. the configuration of the remote server. For Postfix this limit can be configured via 'smtpd_client_new_tls_session_rate_limit' option, for other products please refer to the manual of the product in question on configuration possibilities.