What it is
TLS 1.2 supports dozens of cipher suites, but many were designed before modern cryptographic expectations. Suites such as 0xC023/0xC024, RC4-based options, or any configuration without Elliptic Curve Diffie-Hellman ephemeral (ECDHE) key exchange are now considered weak. If these remain enabled on servers, an attacker can try to negotiate the insecure suite during the handshake, observe unencrypted traffic characteristics, or mount downgrade attacks that peel away protections.
Why it matters
Websites and APIs that advertise weak cipher suites appear secure to users but leave sessions vulnerable to interception. Attackers monitoring public Wi-Fi, compromised routers, or corporate networks can capture traffic and potentially decrypt or tamper with it. Lack of forward secrecy also means that stolen private keys allow decryption of previously recorded sessions. Compliance frameworks (PCI DSS, NIST, UK Cyber Essentials) increasingly require modern AEAD ciphers and deprecate legacy suites, so outdated TLS stacks can jeopardize audits as well as security.
How to reduce risk
- Disable deprecated TLS 1.2 cipher suites and prioritize AEAD options like AES-GCM or CHACHA20-POLY1305.
- Enforce forward secrecy by requiring ECDHE key exchange and disabling RSA key transport.
- Remove support for TLS 1.0 and 1.1 entirely, and monitor for downgrade attempts.
- Regularly audit TLS configurations with automated scanners (FYND, Qualys SSL Labs, Mozilla Observatory).
- Use modern libraries or managed load balancers that ship with secure defaults and rapid updates.