Monday, May 8, 2017

Vulnerability Spotlight: WolfSSL library X.509 Certificate Text Parsing Code Execution Vulnerability

Discovered by Aleksandar Nikolic of Cisco Talos

Overview

Talos is disclosing TALOS-2017-0293 / CVE 2017-2800, a code execution vulnerability in WolfSSL. WolfSSL is a lightweight SSL/TLS library targeted specifically for embedded and RTOS (Real-Time Operating System) environments, due largely to its small size and performance. WolfSSL is used in a wide range of products including ICS and IoT devices.

This particular vulnerability is related to the use of x.509 certificates and the code that deals with string fields in DER certificates. Specifically the code responsible for parsing 'commonName', 'countryName', 'localityName', 'stateName', 'orgName', and 'orgUnit'. A specially crafted x.509 certificate can cause a single out-of-bounds overwrite that could result in certificate validation issues, denial of service, or remote code execution. To trigger this vulnerability, the adversary needs to supply a malicious x.509 certificate to either the server or client application that is making use of this library. The full details surrounding the vulnerability are available here.

Coverage

The following Snort rules will detect exploitation attempts. Note that additional rules may be released at a future date, and current rules are subject to change pending additional vulnerability information. For the most current rule information, please refer to your FireSIGHT Management Center or Snort.org.

Snort Rule: 42000

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