Thursday, 9 July 2015

OpenSSL vulnerability, Severity: High, CVE-2015-1793

On June 11, an updated version of OpenSSL was released. It was disclosed earlier today that it contained a serious certificate validation error (CVE-2015-1793). Luckily, the vulnerability was discovered quickly enough (two weeks ago) and once made it was made public today a patch was also made available.
During certificate verification, OpenSSL (starting from version 1.0.1n and 1.0.2b) 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, such as the CA flag, enabling them to use a valid leaf certificate to act as a CA and "issue" an invalid certificate.

This issue will impact any application that verifies certificates including SSL/TLS/DTLS clients and SSL/TLS/DTLS servers using client authentication. 

This issue affects OpenSSL versions 1.0.2c, 1.0.2b, 1.0.1n and 1.0.1o.
OpenSSL 1.0.2b/1.0.2c users should upgrade to 1.0.2d
OpenSSL 1.0.1n/1.0.1o users should upgrade to 1.0.1p

Please note that support for OpenSSL versions 1.0.0 and 0.9.8 will cease on 31st December 2015. No security updates for these releases will be provided after that date. Users of these releases are advised to upgrade their OpenSSL implementations to the latest version. 

It is strongly suggested to update OpenSSL implementations to the latest version.

If you would like to run a quick check on your network for SSL implementations you can do that by using nmap: 
nmap -sV -Pn --script ssl-enum-ciphers --version-intensity 2 [IP/CIDR]

Are you using Nessus? If you do, make sure you update to the latest version (6.4.1) and update your plugins: nessuscli.exe update --plugins-only
Use Plugin IDs 84636/7 for testing.

Maybe it is time for you to look into into the s2n, which is a new open source TLS implementation. This implementation avoids the rarely used options and extensions of the TLS implementation. Consequently, it consists of approximately 6000 lines of code and makes it a lot easier to review. As it stands at the moment, s2n has passed three external security evaluations and penetration tests.

No comments:

Post a Comment