Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')

This flaw, often called an algorithm downgrade attack, happens because the negotiation process doesn't prioritize the most secure mutual option. Attackers can exploit this by interfering with the handshake to force the use of a broken or outdated algorithm, making subsequent attacks like decryption or spoofing significantly easier. From a developer's perspective, the danger is that the system operates without alerting users to the reduced protection. For example, if an attacker forces a connection to use basic encryption instead of strong AES-256, they can later decrypt traffic with minimal effort, bypassing the intended security entirely. The core fix is to implement negotiation logic that always selects the strongest mutually-available algorithm and rejects weak fallbacks.