[R1] Cisco Security Manager and Prime LMS Java Deserialization Remote Code Execution

In late 2015, Cisco generated a long list of products that might be vulnerable to Java deserialization attacks. The list was, and still is, broken down into three categories: Under Investigation, Confirmed Affected, and Confirmed Not Affected.

Due to the severity of these vulnerabilities Tenable began investigating as well. While investigating Cisco Security Manager researchers came upon this code in SecretServiceServlet.class:

public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
{
    boolean debug = false;
    HttpSession session = request.getSession();
    String context = session.getId();
    if (debug)
    {
        System.out.println("SecretService: Context = " + context);
    }
    
    DataBlob blob = null;
    ServletInputStream sin;
    if ((sin = request.getInputStream()) != null)
    {
        try
        {
            ObjectInputStream ois = new ObjectInputStream(new BufferedInputStream(sin));
            blob = (DataBlob)ois.readObject();
        }
        catch (Exception e)
        {
            if (debug)
            {
                System.out.println("SecretService: Exception thrown deserializing data blob: " + e);
             }
        }
    }
}

This code handles HTTP POST requests to:

https://<target>/CSCOnm/servlet/com.cisco.nm.cmf.servlet.SecretServiceServlet

The above is a classic example of deserialization of untrusted data. The method loads the HTTP payload into an ObjectInputStream and executes readObject(). Because Apache Commons Collection 3.2 is on the classpath an unauthenticated remote attacker can gain execution using one of ysoserial's Commons Collections gadgets.

Interestingly, this exact same code and HTTP endpoint also exists in Cisco Prime LAN Management Solution. However, the LMS version we were analyzing had an ancient version of Commons Collections on the classpath. Making remote code execution impossible. Further investigation into LMS revealed that it exposes an RMI Registry that does have Apache Commons Collections 3.2 on the classpath. Therefore, we were able to exploit LMS by a deserialization attack through the RMI registry.

Tenable immediately informed Cisco of these vulnerabilities.