OpenSSL Alternative Chains Certificate Forgery (Aug 3, 2015)

A few weeks ago, OpenSSL released patches that fix sereral vulnerabilities. Among the vulnerabilities, the “Alternative Chains Certificate Forgery” can lead to man-in-the-middle (MITM) attacks.

This MITM vulnerability affects OpenSSL versions 1.0.2c, 1.0.2b, 1.0.1n and 1.0.1o. During certificate verification, OpenSSL will attempt to find an alternative certificate chain if the first attempt to build such a chain fails. An error in the implementation of this logic can mean that an attacker could cause certain checks on untrusted certificates to be bypassed, enabling them to use a valid leaf certificate to act as a CA and “issue” an invalid certificate.

The vulnerability is referred by CVE as CVE-2015-1793.

Dell SonicWALL has released an IPS signature to detect and block exploitation attempts targeting this vulnerability. The signature is listed below:

• 11041 OpenSSL X509_verify_cert Function Security Bypass

Dell SonicWALL has observed several attack attempts in the past week:

Targeted IPs affected by the vulnerability:

Security News

The SonicWall Capture Labs Threat Research Team gathers, analyzes and vets cross-vector threat information from the SonicWall Capture Threat network, consisting of global devices and resources, including more than 1 million security sensors in nearly 200 countries and territories. The research team identifies, analyzes, and mitigates critical vulnerabilities and malware daily through in-depth research, which drives protection for all SonicWall customers. In addition to safeguarding networks globally, the research team supports the larger threat intelligence community by releasing weekly deep technical analyses of the most critical threats to small businesses, providing critical knowledge that defenders need to protect their networks.