CVE Number – CVE-2018-1000520
A vulnerability in the mbedtls_ssl_get_verify_result() function of ARM mbed Transport Layer Security (TLS) could allow an unauthenticated, remote attacker to cause a targeted system to accept an arbitrary Elliptic Curve Digital Signature Algorithm (ECDSA) signed certificate.
The vulnerability exists in the mbedtls_ssl_get_verify_result() function of the affected software and is due to improper validation of signed certificates. An attacker on a peer system could use a negotiated cipher suite of an Elliptic Curve Diffie-Hellman (ECDH) key exchange and Rivest-Shamir-Adleman (RSA) signed certificate (TLS-ECDH-RSA-*) to cause the targeted system to accept an arbitrary ECDSA signed certificate. A successful exploit could be used to conduct further attacks.
Proof-of-concept (PoC) code that demonstrates an exploit of this vulnerability is publicly available.
ARM confirmed the vulnerability; however, software updates are not available.
To exploit this vulnerability, the attacker may need access to the same trusted, internal network in which the targeted system resides. This access requirement may reduce the likelihood of a successful exploit.
Reports indicate that this vulnerability may also be present in versions later than mbed TLS 2.7.0.
Administrators are advised to contact the vendor regarding future updates and releases.
Administrators are advised to allow only trusted users to have network access.
Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators can help protect affected systems from external attacks by using a solid firewall strategy.
Administrators are advised to monitor affected systems.
ARM released an issue report at the following link: issue #1561
At the time this alert was first published, ARM had not release software updates to address this vulnerability.