DROWN is a serious vulnerability that affects HTTPS and other services that rely on SSL and TLS, some of the essential cryptographic protocols for Internet security. These protocols allow everyone on the Internet to browse the web, use email, shop online, and send instant messages without third-parties being able to read the communication. DROWN allows attackers to break the encryption and read or steal sensitive communications, including passwords, credit card numbers, trade secrets, or financial data.
A server is vulnerable to DROWN if:
- It allows SSLv2 connections OR
- Its private key is used on any other server that allows SSLv2 connections, even for another protocol.
To protect against DROWN, server operators need to ensure that their private keys are not used anywhere with server software that allows SSLv2 connections. Users can avoid this issue by disabling the SSLv2 protocol in all their SSL/TLS servers, if they've not done so already. Disabling all SSLv2 ciphers is also sufficient, provided the patches for CVE-2015-3197 (fixed in OpenSSL 1.0.1r and1.0.2f) have been deployed.