ARM mbed TLS RSA Decryption Plaintext Recovery Vulnerability

CVE Number – CVE-2018-19608

A vulnerability in ARM mbed TLS could allow a local attacker to access sensitive information on a targeted system.

The vulnerability is due to improper restrictions on timing and memory access variations on a cipher suite that uses Rivest, Shamir, and Adleman (RSA) Public-Key Cryptography Standard #1 (PKCS #1) Version 1.5 decryption whose name contains RSA, but not containing Diffie–Hellman (DH), Ephemeral Diffie-Hellman (DHE), Elliptic Curve Diffie–Hellman (ECDH), or Ephemeral Elliptic Curve Diffie-Hellman (ECDHE). An attacker who is able to execute arbitrary code on a targeted system performing an RSA decryption could exploit this vulnerability to conduct a Bleichenbacher-like oracle attack on the system. An exploit could allow the attacker to access sensitive information by recovering the plain text of the RSA decrypted information. 

Proof-of-concept (PoC) code that demonstrates an exploit of this vulnerability is publicly available. 

ARM has confirmed the vulnerability and released software updates.

Analysis

• To exploit this vulnerability, the attacker must have user-level access to the targeted system. This access requirement could reduce the likelihood of a successful exploit.

Safeguards

• Administrators are advised to apply the appropriate updates.
  
  Administrators are advised to allow only trusted users to access local systems.
  
  Administrators are advised to allow only privileged users to access administration or management systems.
  
  Administrators are advised to monitor critical systems.

Vendor Announcements

• ARM has released a security advisory and release notes at the following links: Mbed TLS Security Advisory 2018-03 and Mbed TLS 2.14.1, 2.7.8 and 2.1.17 released

Fixed Software

• ARM has released software updates at the following link: Mbed TLS 2.14.1, 2.7.8 and 2.1.17