• The SSL 3.0 Vulnerability – POODLE Bug (AKA POODLEbleed)

        Oct 20 2017, 8:27 PM

        by Brook Chelmo 4


        A bug has been found in the Secure Sockets Layer (SSL) 3.0 cryptography protocol (SSLv3) which could be exploited to intercept data that’s supposed to be encrypted between computers and servers. Three Google security researchers discovered the flaw and detailed how it could be exploited through what they called a Padding Oracle On Downgraded Legacy Encryption (POODLE) attack (CVE-2014-3566).

        (Updated Dec. 9, 2014) Recently, a new variant of the POODLE vulnerability (CVE-2014-8730) was found to affect even versions of TLS, the successor to the SSL protocol.  This new vulnerability works against sites that use load balancers that have incorrectly implemented encryption padding checks, and may affect around 10% of servers.  Certain models of F5 and A10 load balancers are susceptible, and as part of best practices we recommend that users apply vendor-supplied patches as they become available.

        It is important to note that this is NOT a flaw in SSL certificates, their private keys, or their design but in the old SSLv3 protocol.  SSL Certificates are not affected and customers with certificates on servers supporting SSL 3.0 do not need to replace them.

        It’s believed to not be as serious as the Heartbleed bug in OpenSSL, since the attacker needs to have a privileged position in the network to exploit the latest.  The usage of Hotspots, public Wi-Fi, makes this attack a real problem. This type of attack falls into the “Man-in-the-middle” category. 


        While SSL 3.0 was introduced in 1996, it is currently supported by nearly 95% of Web browsers according to Netcraft’s latest report.  Many Transport Layer Socket (TLS) clients downgrade their cryptography protocol to SSL 3.0 when working with legacy servers. According to Google, an attacker that controls the network between the computer and server could interfere with the handshake process used to verify which cryptography protocol the server can accept using a “protocol downgrade dance”. This will force computers to use the older SSL 3.0 protocol to protect data that is being sent. Attackers can then exploit the bug by carrying out a man-in-the-middle (MITM) attack to decrypt secure HTTP cookies, which could let them steal information or take control of the victim’s online accounts.  Although, at the time to writing, webmasters have been disabling SSL 3.0 and moving to TLSv1 and above at a rapid pace, there still remains a lot of work to be done.  If Heartbleed taught us anything, it’s that the largest companies act fast while many small companies drag their heels in patching critical vulnerabilities. 

        What Businesses Need to Do

        In order to mitigate the bug there are a few courses of action:

        1. Check to see if your webservers are vulnerable using our free SSL Toolbox.
        2. Disable SSL 3.0 altogether, or disable SSL 3.0 CBC-mode ciphers
        3. A cloud-based Web Application Firewall can help protect against this kind of vulnerability.  For more information please visit our website.
        4. Be leery of any spam messages from scammers trying to capitalize on uncertainty and a lack of technical knowledge.
        5. If applicable, implement F5’s patch.  For information on A10 Networks, please click here for their patch.

        My fellow colleague Christoffer Olausson gives a few tips on how to fix this on Apache:

        > SSLProtocol All -SSLv2 -SSLv3                   <- Removes SSLv2 and SSLv3

        > apachectl configtest                                   <- Test your configuration

        > sudo service apache restart                      <- Restart server

        At the time of writing Google and Mozilla have either removed SSL 3.0 support from their browsers or are in the process of doing so.

        What End-Users Need to Do

        For end-users accessing websites Symantec recommends:

        1. Check to see if SSL 3.0 is disabled on your browser (for example, in Internet Explorer it is under Internet Options, Advanced Settings).
        2. Avoid MITM attacks by making sure “HTTPS” is always on the websites you visit.
        3. Monitor any notices from the vendors you use regarding recommendations to update software or passwords.
        4. Avoid potential phishing emails from attackers asking you to update your password – to avoid going to an impersonated website, stick with the official site domain.

        More Information

        Symantec has published knowledge base articles on the subject for your reference.  See below:

        Symantec Managed PKI for SSL Users

        Symantec Trust Center/Trust Center Enterprise Users

        Stay Connected

        Stay connected with us for more updates on this vulnerability and others.  Follow us on Twitter, Facebook, or visit our technical forums for issues with managing SSL and code-signing certificates.

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