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Date: Wed, 3 May 2017 18:23:09 +0200
From: Pali Rohár <>
Subject: MySQL - Again Riddle vulnerability (public disclosure)


The Riddle vulnerability (CVE-2017-3305) we have it there again. 

So what happened?

In 2015 was discovered BACKRONYM vulnerability (CVE-2015-3152) which 
allowed an attacker to downgrade and snoop on the SSL encrypted 
connection between MySQL client and server. Oracle claimed it was fixed 
in MySQL 5.5.49. Later in February 2017 I discovered The Riddle 
vulnerability (CVE-2017-3305) which allowed an attacker to do man in the 
middle attack. Oracle claimed it was fixed in MySQL 5.5.55.

And now in April 2017 I found out that it is still not fixed in MySQL 
5.5.55 properly and I named this defect Again Riddle. Basically fix for 
The Riddle in 5.5.55 introduced Again Riddle.

And what is the problem?

If MySQL client library is compiled from source code 
without SSL support via cmake switch -DWITH_SSL=OFF, then all SSL 
related functions from return success (non-error) 
value. And function mysql_real_connect() from connects 
to MySQL server via plain text protocol, even if client enforced SSL 
mode with certificate verification. Which means that function for 
enforcing SSL mode does nothing if is compiled without 
SSL support. So attacker can do exactly same what for The Riddle 

So every application which links to and require SSL 
encryption of MySQL protocol is affected.

I contacted Oracle, MariaDB and Percona security teams about this 
problem and after discussion we scheduled public disclosure to May 3.

Oracle decided that this Again Riddle vulnerability would not have CVE 
identifier and would be part of original The Riddle vulnerability 

I'm not sure if this is correct decision, as MariaDB 5.5 was not 
affected by The Riddle vulnerability, but is affected by Again Riddle.

I was told that prebuild binaries are not affected as they are compiled 
with SSL support, but lot of distributions compile libraries from source 
code by their own which means they could be affected.

I prepared POC program written in C to verify if system installed library is vulnerable or not. You can find it on the 
new Again Riddle website together with some Q&A:

Pali Rohár

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