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POODLE Attack on SSL 3.0

POODLE Attack on SSL 3.0

Description

This vulnerability indicates that the server is susceptible to POODLE attacks, which exploit fundamental design flaws in SSL 3.0 padding validation to decrypt encrypted communications through padding oracle attacks combined with protocol downgrade.

POODLE (Padding Oracle On Downgraded Legacy Encryption) occurs when SSL 3.0 implementations fail to properly validate block cipher padding in CBC mode. The padding is not covered by the message authentication code, allowing attackers to manipulate encrypted data and use server responses as an oracle to decrypt secrets one byte at a time.

How It Works:

  1. Attacker forces protocol downgrade from TLS to vulnerable SSL 3.0
  2. Malicious JavaScript makes repeated requests with controlled padding
  3. Server responses reveal padding validation results as oracle information
  4. Systematic manipulation extracts sensitive data like cookies and tokens

Requirements:

  • SSL 3.0 support with CBC cipher suites
  • Man-in-the-middle network access
  • Protocol downgrade capability
  • JavaScript execution in victim's browser

Example Scenario: An attacker on public WiFi forces a victim's browser to downgrade from TLS 1.2 to SSL 3.0 during login to a banking website. Through injected JavaScript making thousands of crafted requests, the attacker exploits SSL 3.0's weak padding validation to decrypt the session cookie byte-by-byte in under 10 minutes, gaining complete access to the victim's banking account.

The attack demonstrates why SSL 3.0 is fundamentally insecure and must be completely disabled, leading to session hijacking, data theft, and compliance violations.

Recommendation

To mitigate POODLE attacks:

Primary Defense - Disable SSL 3.0:

# Nginx configuration
ssl_protocols TLSv1.2 TLSv1.3;
# Apache configuration
SSLProtocol -all +TLSv1.2 +TLSv1.3

Implement TLS_FALLBACK_SCSV:

  • Prevents protocol downgrade attacks
  • Supported in OpenSSL 1.0.1j+ and modern TLS libraries
  • Allows safe fallback without forcing SSL 3.0

Browser Protection:

  • Modern browsers disable SSL 3.0 by default
  • Ensure browsers are up-to-date
  • Consider implementing Content Security Policy

Alternative Mitigations (if SSL 3.0 required):

  • Disable CBC cipher suites in SSL 3.0
  • Implement anti-POODLE record splitting
  • Use only RC4 ciphers

By completely disabling SSL 3.0 and implementing TLS_FALLBACK_SCSV, organizations eliminate POODLE attack vectors while maintaining secure encrypted communications.

Standards

  • SOC2_CONTROLS:
    • CC_6_7
    • CC_7_1
  • CCPA:
    • CCPA_1798_150
  • GDPR:
    • ART_32
  • PCI_STANDARDS:
    • REQ_4_1
    • REQ_6_2
    • REQ_11_3