DROWNAttack

DROWN Attack is a security vulnerability in some TLS and SSL servers. Its full name is Decrypting RSA with Obsolete and Weakened eNcryption, and it is sometimes referred to by the acronym DROWN. The attack arises when a server supports the older SSLv2 protocol and shares an RSA private key with other servers that handle TLS connections. Under these conditions, an attacker who can observe network traffic to the TLS service may be able to decrypt otherwise encrypted communications.

In practical terms, the DROWN vulnerability relies on cross-protocol weaknesses between SSLv2 and modern TLS services that reuse the same private key. An attacker can exploit information gleaned from SSLv2 handshakes on the shared key to facilitate decrypting TLS traffic. The attack does not require breaking the TLS engine itself and can be performed remotely with access to the network traffic, though it depends on specific server configurations and key management practices.

The vulnerability was disclosed publicly in 2016. It prompted widespread advisories and software updates as many servers were found to be at risk due to SSLv2 support or key reuse across services. The overall risk varies by deployment and configuration, with higher risk where private keys are shared among multiple servers and SSLv2 support remains enabled.

Mitigation strategies focus on removing SSLv2 support, avoiding RSA key exchange vulnerabilities, and practicing strict key management. Recommended steps include disabling SSLv2 across all services, using unique private keys per service, enabling forward secrecy with modern ciphers, and applying vendor patches to TLS libraries. Regular key rotation and configuration reviews further reduce exposure to DROWN-like attacks.