CVE-2024-45159

What it actually does

Incorrect clearing of MBEDTLS_X509_BADCERT_KEY_USAGE and MBEDTLS_X509_BADCERT_EXT_KEY_USAGE bits in mbedtls_ssl_get_verify_result() for TLS 1.3 optional client authentication allows certificates lacking proper keyUsage or extKeyUsage to be treated as valid for client auth.

Why it matters to the business

Attackers may gain unauthorized access to services that rely on TLS client certificate authentication, potentially exposing sensitive data or systems, though low exploit maturity and EPSS reduce immediate widespread risk.

How an attack unfolds

An attacker obtains a certificate valid for non-TLS purposes, connects to a vulnerable TLS 1.3 server configured for optional client authentication, presents the certificate during the handshake, and the flawed verification allows the connection to proceed as authenticated.

How to fix it

Upgrade Mbed TLS to version 3.6.1 or apply commit 71c569d44bf3a8bd53d874c81ee8ac644dd6e9e3; update affected mysql-client (Bitnami) packages to version 10.3.35 or later.

How to confirm the fix worked

Confirm deployed version is 3.6.1 or newer, then test handshake behavior using a certificate with non-client-auth keyUsage to verify MBEDTLS_X509_BADCERT_KEY_USAGE is now correctly reported.

Typical attack path

1. Acquire a certificate whose keyUsage or extKeyUsage does not permit TLS client authentication
2. Initiate a TLS 1.3 handshake against a server with optional client authentication enabled
3. Supply the certificate in the ClientCertificate message
4. Bypass intended authorization checks due to incorrect verify result
5. Proceed with authenticated session to access protected resources

How to detect it

Review TLS handshake logs for successful client authentications that used certificates later found to lack proper keyUsage values; correlate with certificate issuance records.

What your security team should do

• Apply the listed fixed versions immediately on all TLS 1.3 servers using optional client authentication
• Audit configurations to disable optional client auth where possible until patched
• Monitor for certificate-related authentication anomalies in application logs