Zero-friction vulnerability management platform

Mageni eases for you the vulnerability scanning, assessment, and management process. It is free and open-source.

Install Now

Available for macOS, Windows, and Linux

App screenshot

Diffie-Hellman Ephemeral Key Exchange DoS Vulnerability (SSL/TLS, D(HE)ater)

Information

Severity

Severity

Medium

Family

Family

Denial of Service

CVSSv2 Base

CVSSv2 Base

5.0

CVSSv2 Vector

CVSSv2 Vector

AV:N/AC:L/Au:N/C:N/I:N/A:P

Solution Type

Solution Type

Mitigation

Created

Created

11 months ago

Modified

Modified

11 months ago

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.

Common Vulnerabilities and Exposures (CVE)