CVE-2016-5736 in BIG-IP
Summary
by MITRE
The default configuration of the IPsec IKE peer listener in F5 BIG-IP LTM, Analytics, APM, ASM, and Link Controller 11.2.1 before HF16, 11.4.x, 11.5.x before 11.5.4 HF2, 11.6.x before 11.6.1, and 12.x before 12.0.0 HF2; BIG-IP AAM, AFM, and PEM 11.4.x, 11.5.x before 11.5.4 HF2, 11.6.x before 11.6.1, and 12.x before 12.0.0 HF2; BIG-IP DNS 12.x before 12.0.0 HF2; BIG-IP Edge Gateway, WebAccelerator, and WOM 11.2.1 before HF16; BIG-IP GTM 11.2.1 before HF16, 11.4.x, 11.5.x before 11.5.4 HF2, and 11.6.x before 11.6.1; and BIG-IP PSM 11.4.0 through 11.4.1 improperly enables the anonymous IPsec IKE peer configuration object, which allows remote attackers to establish an IKE Phase 1 negotiation and possibly conduct brute-force attacks against Phase 2 negotiations via unspecified vectors.
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Analysis
by VulDB Data Team • 09/13/2022
The vulnerability described in CVE-2016-5736 represents a critical security flaw in the IPsec IKE implementation within F5 BIG-IP systems across multiple product lines including Local Traffic Manager Analytics APM ASM and Link Controller. This issue stems from the default configuration of the IPsec IKE peer listener which inadvertently enables anonymous IPsec IKE peer configuration objects. The flaw specifically affects versions of F5 BIG-IP software prior to certain hotfix releases, creating a persistent security risk that can be exploited by remote attackers without authentication. The vulnerability operates at the network security protocol level where IPsec IKE Phase 1 and Phase 2 negotiations are handled, making it particularly dangerous for organizations relying on IPsec for secure communications.
The technical implementation of this vulnerability involves the improper enabling of anonymous IPsec IKE peer configuration objects within the BIG-IP system's default settings. This configuration allows attackers to initiate IKE Phase 1 negotiations without requiring proper authentication credentials, which then potentially enables brute-force attacks against Phase 2 negotiations. The anonymous configuration object essentially removes the requirement for identity verification during the initial phase of IPsec tunnel establishment, creating an attack surface that can be exploited to conduct unauthorized access attempts. This flaw aligns with CWE-284 Access Control Issues as it provides unauthorized access to network security protocols through improper configuration settings. The vulnerability can be classified under ATT&CK technique T1071.001 Application Layer Protocol DNS for exploitation pathways involving DNS-based attacks and T1566 Impersonation for the unauthorized establishment of secure connections.
The operational impact of this vulnerability extends beyond simple network access issues as it fundamentally compromises the integrity of IPsec security implementations within affected F5 BIG-IP systems. Organizations using these systems for secure remote access, site-to-site connections, or any IPsec-based security measures face significant risks including unauthorized tunnel establishment, potential data interception, and compromised network security posture. The vulnerability can be exploited by attackers to conduct prolonged brute-force attacks against Phase 2 negotiations, potentially leading to complete tunnel compromise and unauthorized access to protected network segments. The exposure affects multiple F5 product lines including AAM AFM PEM DNS Edge Gateway WebAccelerator WOM GTM and PSM, indicating a widespread impact across the F5 BIG-IP platform ecosystem. Attackers can leverage this vulnerability to establish unauthorized secure connections, potentially leading to man-in-the-middle attacks or complete network infiltration depending on the network architecture and security controls in place.
Mitigation strategies for CVE-2016-5736 require immediate implementation of configuration changes to disable anonymous IPsec IKE peer configurations and apply the appropriate vendor hotfixes for affected versions. Organizations should review their IPsec configurations to ensure that anonymous peer objects are disabled and that proper authentication mechanisms are enforced for all IKE negotiations. The recommended approach includes applying the specific hotfixes provided by F5 for each affected product line and version, as well as implementing network segmentation to limit the attack surface. Security teams should also monitor for unauthorized IKE Phase 1 negotiations and implement network-based intrusion detection systems to identify potential exploitation attempts. Additionally, organizations should conduct comprehensive security audits of their IPsec implementations to ensure that all configurations align with security best practices and that no anonymous peer configurations remain active. The implementation of these mitigations should follow industry standards for network security configuration management and should be part of a broader security posture assessment to prevent similar vulnerabilities from existing in other network security protocols.