CVE-2024-5814

What it actually does

A TLS 1.3 client that supports protocol downgrade skips full parsing of the ServerHello, allowing a malicious TLS 1.2 server to force negotiation of a ciphersuite the client did not agree to.

Why it matters to the business

Attackers can weaken the encryption of connections from affected Android devices, increasing the risk of data exposure on networks where an attacker controls the server or can intercept traffic.

How an attack unfolds

An attacker positions a malicious TLS 1.2 server that responds to a TLS 1.3 client with a crafted ServerHello; because the client does not fully parse the message, it accepts a ciphersuite outside its negotiated set and completes the connection under the attacker's chosen parameters.

How to fix it

Update affected Android devices to the versions that contain the fix released on 2023-01-01 for Android 10, 11, 12, 12L, and 13. Apply the latest security patches through the vendor's update mechanism and disable TLS downgrade support where possible.

How to confirm the fix worked

Confirm the device is running a patched Android release listed in the fixed versions; inspect the TLS client implementation to ensure ServerHello extensions are fully parsed before ciphersuite selection; test handshake behavior against a controlled malicious TLS 1.2 server.

Typical attack path

1. Attacker deploys or compromises a TLS 1.2 server reachable by the target client
2. Client initiates a TLS 1.3 handshake with downgrade support enabled
3. Server returns a ServerHello that omits or manipulates extensions the client fails to validate
4. Client accepts the offered ciphersuite and completes the handshake
5. Attacker observes or manipulates traffic protected by the weaker ciphersuite

How to detect it

Examine TLS handshake logs on clients and network sensors for unexpected ciphersuite selections or protocol version downgrades that deviate from configured client preferences; review application-layer logs for connections completed after malformed ServerHello messages.

What your security team should do

• Prioritize patching Android devices to the fixed releases from 2023-01-01
• Review mobile device management policies to enforce current security patch levels
• Monitor vendor advisories for any additional TLS client updates
• Consider disabling protocol downgrade capabilities in client configurations where feasible