AIKIDO-2025-10219
Mbed-TLS.mbedtls is vulnerable to Improper Certificate Validation
95
Critical Risk
This Affects:
Mbed-TLS.mbedtlsTL;DR
Affected versions of this package are vulnerable to improper certificate validation during optional TLS 1.3 client authentication. In Mbed TLS 3.6.0, the function mbedtls_ssl_get_verify_result() fails to correctly report missing digitalSignature or clientAuth flags in the client's certificate, returning 0 even when the certificate should be considered invalid. This allows an attacker to use a certificate valid for other purposes (but not for client authentication) to bypass verification checks. This issue does not affect mandatory authentication, TLS 1.2, or TLS 1.3 server authentication.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range.
Background info
Mbed-TLS.mbedtls is vulnerable to Improper Certificate Validation in versions 3.2.0 - 3.6.0.
How to fix this
Affected users should upgrade to Mbed TLS 3.6.1. As a workaround, servers using optional client authentication should enforce TLS 1.2 by setting the maximum TLS version to MBEDTLS_SSL_VERSION_TLS1_2.
Links
GitHub Releases
Other
mbed-tls.readthedocs.io/en/latest/security-advisories/mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2024-08-3/
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SOC 2Compliant
ISO 27001Compliant