CVE-2017-6168 in BIG-IP
Summary
by MITRE
On BIG-IP versions 11.6.0-11.6.2 (fixed in 11.6.2 HF1), 12.0.0-12.1.2 HF1 (fixed in 12.1.2 HF2), or 13.0.0-13.0.0 HF2 (fixed in 13.0.0 HF3) a virtual server configured with a Client SSL profile may be vulnerable to an Adaptive Chosen Ciphertext attack (AKA Bleichenbacher attack) against RSA, which when exploited, may result in plaintext recovery of encrypted messages and/or a Man-in-the-middle (MiTM) attack, despite the attacker not having gained access to the server's private key itself.
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Analysis
by VulDB Data Team • 12/25/2024
The vulnerability described in CVE-2017-6168 represents a critical cryptographic flaw affecting F5 BIG-IP load balancer appliances running specific versions of the BIG-IP software. This vulnerability specifically targets virtual servers configured with Client SSL profiles and exploits a weakness in the RSA encryption implementation that allows attackers to perform adaptive chosen ciphertext attacks, commonly known as Bleichenbacher attacks. The flaw exists in versions 11.6.0 through 11.6.2, 12.0.0 through 12.1.2 HF1, and 13.0.0 through 13.0.0 HF2, with respective fixes released in subsequent hotfixes. The vulnerability stems from improper implementation of RSA padding verification during SSL/TLS handshakes, creating a side-channel attack surface that undermines the fundamental security properties of the encrypted communications.
The technical nature of this vulnerability falls under CWE-310, which specifically addresses cryptographic weaknesses in padding schemes and key management practices. The attack exploits the deterministic nature of certain RSA padding implementations, particularly PKCS#1 v1.5 padding, where an attacker can craft specific ciphertexts and observe the server's responses to determine the plaintext of encrypted messages. This adaptive approach allows attackers to iteratively recover sensitive information through careful analysis of error responses during the decryption process, effectively bypassing the security provided by RSA encryption. The vulnerability is particularly dangerous because it operates at the SSL/TLS protocol level, meaning that even though the attacker cannot directly access the private key, they can still compromise the confidentiality of communications by exploiting the flawed cryptographic implementation.
The operational impact of this vulnerability extends far beyond simple data confidentiality breaches, as it enables sophisticated man-in-the-middle attacks that can compromise entire communication channels. Attackers can exploit this weakness to decrypt sensitive information such as session tokens, authentication credentials, and business-critical data transmitted through the affected virtual servers. The vulnerability affects organizations that rely on F5 BIG-IP appliances for SSL termination and load balancing, potentially exposing financial transactions, personal data, and proprietary information to unauthorized access. Organizations using these vulnerable versions face significant risk of data breaches, regulatory compliance violations, and potential legal consequences due to the exposure of sensitive communications. The attack vector requires minimal privileges and can be executed remotely, making it particularly attractive to threat actors seeking to exploit enterprise SSL infrastructure.
Mitigation strategies for this vulnerability should include immediate deployment of the vendor-provided hotfixes and patches for each affected version range, specifically 11.6.2 HF1, 12.1.2 HF2, and 13.0.0 HF3. Organizations should also consider implementing additional security controls such as certificate pinning, enhanced monitoring of SSL/TLS handshake behaviors, and network segmentation to limit the impact of potential exploitation. Security teams should conduct thorough vulnerability assessments of their BIG-IP deployments to identify all affected virtual servers and ensure proper patch management processes are in place. The ATT&CK framework categorizes this vulnerability under T1046 Network Service Scanning and T1566 Credential Access through Network Sniffing, highlighting the need for comprehensive network security monitoring and incident response capabilities. Organizations should also consider upgrading to supported BIG-IP versions that have addressed this cryptographic weakness and implement regular security assessments to identify similar vulnerabilities in their infrastructure.