CVE-2019-6593 in BIG-IP
Summary
by MITRE
On BIG-IP 11.5.1-11.5.4, 11.6.1, and 12.1.0, a virtual server configured with a Client SSL profile may be vulnerable to a chosen ciphertext attack against CBC ciphers. When exploited, this may result in plaintext recovery of encrypted messages through a man-in-the-middle (MITM) attack, despite the attacker not having gained access to the server's private key itself. (CVE-2019-6593 also known as Zombie POODLE and GOLDENDOODLE.)
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Analysis
by VulDB Data Team • 07/19/2023
The vulnerability identified as CVE-2019-6593 represents a critical security flaw in F5 BIG-IP appliances affecting versions 11.5.1 through 11.5.4, 11.6.1, and 12.1.0. This vulnerability operates under the broader category of cryptographic weaknesses and is specifically classified as a chosen ciphertext attack against CBC (Cipher Block Chaining) ciphers. The flaw manifests when a virtual server is configured with a Client SSL profile, creating a pathway for attackers to exploit the SSL/TLS implementation in ways that bypass traditional encryption protections.
The technical mechanism behind this vulnerability stems from the improper handling of padding in CBC cipher modes during the SSL/TLS handshake process. Attackers can manipulate encrypted traffic to recover plaintext information through a man-in-the-middle position, exploiting the specific implementation details of the F5 BIG-IP SSL termination capabilities. This vulnerability is particularly dangerous because it allows for plaintext recovery without requiring access to the server's private key, making it distinct from typical key-extraction attacks and aligning with the broader category of padding oracle attacks that have been documented in various cryptographic implementations.
The operational impact of CVE-2019-6593 extends beyond simple data confidentiality breaches, as it enables sophisticated attack vectors that can compromise sensitive information flowing through the affected systems. Organizations using F5 BIG-IP appliances with the vulnerable configurations face potential exposure to data interception, session hijacking, and credential theft through this chosen ciphertext attack mechanism. The vulnerability's classification under both Zombie POODLE and GOLDENDOODLE monikers indicates its relationship to previous SSL/TLS vulnerabilities, particularly those related to POODLE attacks that exploited similar padding oracle weaknesses in SSL implementations. This attack vector represents a significant threat to organizations relying on F5 appliances for SSL termination and secure communications.
Security professionals should consider this vulnerability in the context of broader ATT&CK framework categories including T1046 for network service scanning and T1566 for credential access through social engineering, as the exploitation of this vulnerability often requires initial reconnaissance and positioning within network traffic flows. The vulnerability's classification as a CWE-310 (Cryptographic Issues) indicates fundamental weaknesses in the cryptographic implementation that could be exploited across multiple attack surfaces. Organizations should immediately implement mitigations including disabling CBC cipher suites, upgrading to patched versions of F5 BIG-IP software, and implementing additional network monitoring to detect potential exploitation attempts. The vulnerability also highlights the importance of proper cryptographic protocol implementation and the necessity of regular security assessments to identify similar weaknesses in SSL/TLS implementations that could be exploited through chosen ciphertext attacks.