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Mitigation Instructions for SSL Version 2 and 3 Protocol Detection

Mitigation Instructions for SSL Version 2 and 3 Protocol Detection

SUBJECT: SSL Version 2 and 3 Protocol Detection

TECH STACK: Any system using SSL/TLS for secure communications

DATE(S) ISSUED: 10/12/2005, Updated: 04/04/2022

CRITICALITY: CRITICAL

OVERVIEW:

The remote service encrypts traffic using SSL 2.0 and/or SSL 3.0, which are protocols with known weaknesses. These versions of SSL are affected by several cryptographic flaws, including an insecure padding scheme with CBC ciphers and insecure session renegotiation and resumption schemes. An attacker can exploit these flaws to conduct man-in-the-middle attacks or to decrypt communications between the affected service and clients.

Although SSL/TLS has a secure means for choosing the highest supported version of the protocol, many web browsers implement this in an unsafe way that allows an attacker to downgrade a connection (such as in POODLE). Therefore, it is recommended that these protocols be disabled entirely.

NIST has determined that SSL 3.0 is no longer acceptable for secure communications. As of the date of enforcement found in PCI DSS v3.1, any version of SSL will not meet the PCI SSC's definition of 'strong cryptography'.

SOLUTION:

Steps to Mitigate:

  1. Disable SSL 2.0 and SSL 3.0:

    • Consult your application's documentation to identify the configuration settings for SSL/TLS protocols.
    • Modify the configuration to disable SSL 2.0 and SSL 3.0. Ensure only TLS 1.2 or higher is enabled.

    Example for Apache server configuration (httpd.conf or ssl.conf):

    apache
     
    SSLProtocol -all +TLSv1.2 +TLSv1.3
  2. Use Approved Cipher Suites:

    • Ensure the use of strong, approved cipher suites with TLS 1.2 or higher.

    Example for Apache:

    apache
     
    SSLCipherSuite HIGH:!aNULL:!MD5
  3. Verify Configuration:

    • Use tools like SSL Labs' SSL Test or Nessus to verify that SSL 2.0 and SSL 3.0 are disabled and only TLS 1.2 or higher is supported.
  4. Update Software:

    • Ensure all software, including web servers, mail servers, and application servers, are updated to the latest versions that support TLS 1.2 or higher.

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