Improper Certificate Validation
CVE-2020-36477
Summary
An issue was discovered in Mbed TLS in versions prior to 2.24.0. The verification of "X.509" certificates when matching the expected common name (the cn argument of "mbedtls_x509_crt_verify") with the actual certificate name is mishandled: when the "subjecAltName" extension is present, the expected name is compared to any name in that extension regardless of its type. This means that an attacker could impersonate a 4-byte or 16-byte domain by getting a certificate for the corresponding IPv4 or IPv6 address (this would require the attacker to control that IP address, though).
- HIGH
- NETWORK
- HIGH
- UNCHANGED
- NONE
- NONE
- NONE
- NONE
CWE-295 - Improper Certificate Validation
The authenticity component of a web system stems from the ability to validate “Digital certificates”, which (i) establish trust between two or more entities sharing data over a network; (ii) ensure data at rest and transit is secure from unauthorized access; and (iii) check the identity of the actors that interact with the system. An application with absent or ineffective certificate validation mechanisms allows malicious users, impersonating trusted hosts, to manipulate the communication path between the client and the host, resulting in unauthorized access to data and to the application’s internal environment, and potentially enabling man-in-the-middle attacks.
References
Advisory Timeline
- Published
