Description

Detects if a web server improperly handles TLS_FALLBACK_SCSV, a security mechanism that prevents protocol downgrade attacks. The vulnerability exists when a server accepts a connection with a lower TLS version even when the TLS_FALLBACK_SCSV signal is present, potentially allowing attackers to force connections to use weaker protocol versions.

Detection Strategy

• A vulnerability is reported when all of these conditions are met:

• 1. The server supports multiple TLS versions with the minimum version being lower than TLS 1.2

• 2. A connection attempt is made using the lowest supported TLS version with TLS_FALLBACK_SCSV included in cipher suites

• 3. The server accepts the connection instead of rejecting it with an inappropriate_fallback alert