CVE-2024-30166

What it actually does

Stack buffer over-read of less than 256 bytes in TLS 1.3 server processing of TLS 3.1 ClientHello messages, enabling information disclosure or denial of service.

Why it matters to the business

Attackers could read fragments of server memory containing sensitive data or crash TLS services, disrupting encrypted communications and operations.

How an attack unfolds

An attacker crafts and sends a malicious TLS 3.1 ClientHello to a vulnerable TLS 1.3 server; the server performs an out-of-bounds read on the stack while parsing the message, leaking memory contents or triggering a crash.

How to fix it

Upgrade Mbed TLS to version 3.6.0 or apply the patch corresponding to commit 2ca6c285a0dd3f33982dd57299012dacab1ff206; recompile and redeploy all dependent applications.

How to confirm the fix worked

Confirm the running Mbed TLS version is 3.6.0 or later; perform handshake tests with TLS 3.1 ClientHello messages to verify absence of over-read behavior.

Typical attack path

1. Scan for or identify servers running vulnerable Mbed TLS versions 3.3.0-3.5.2
2. Send a specially crafted TLS 3.1 ClientHello packet
3. Trigger the over-read to obtain leaked memory or cause service denial

How to detect it

Review TLS server logs for malformed ClientHello messages, unexpected process crashes, or memory access violations during TLS 1.3 handshakes; correlate with network traffic showing version 3.1 ClientHello to version 1.3 servers.

What your security team should do

• Immediately upgrade all instances of Mbed TLS to the fixed version
• Prioritize patching of internet-facing TLS servers
• Monitor for unusual TLS handshake failures or server crashes
• Review downstream dependents and rebuild affected binaries