CVE-2015-4637 in BIG-IQ
Summary
by MITRE
The REST API in F5 BIG-IQ Cloud, Device, and Security 4.4.0 and 4.5.0 before HF2 and ADC 4.5.0 before HF2, when configured for LDAP remote authentication and the LDAP server allows anonymous BIND operations, allows remote attackers to obtain an authentication token for arbitrary users by guessing an LDAP user account name.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 05/11/2018
The vulnerability identified as CVE-2015-4637 represents a critical authentication bypass flaw within F5 BIG-IQ and ADC platforms that impacts versions 4.4.0 and 4.5.0 before specific hotfixes. This weakness specifically affects systems configured with LDAP remote authentication mechanisms where the LDAP server permits anonymous BIND operations. The vulnerability stems from insufficient validation of user credentials during the authentication process, creating a pathway for unauthorized access through credential guessing attacks. The flaw operates by exploiting the interaction between the F5 appliance's REST API and LDAP server configuration, allowing attackers to enumerate valid user accounts and subsequently obtain authentication tokens for arbitrary users within the system.
The technical implementation of this vulnerability involves the improper handling of LDAP authentication responses when anonymous BIND is permitted by the directory server. When an attacker submits a username to the REST API endpoint, the system performs LDAP authentication without adequately validating that the user account actually exists or that the authentication attempt is legitimate. This creates a scenario where attackers can systematically guess LDAP user accounts and observe different responses based on whether accounts exist, effectively enabling account enumeration. The vulnerability specifically manifests when the LDAP server allows anonymous BIND operations, which permits unauthenticated access to directory information, making it easier for attackers to determine valid user accounts through response analysis.
The operational impact of CVE-2015-4637 is severe and multifaceted, as it enables attackers to gain unauthorized access to privileged accounts within the F5 appliance environment. Successful exploitation allows attackers to obtain authentication tokens that provide full administrative access to the system, potentially compromising the entire network infrastructure managed by the BIG-IQ appliance. This vulnerability directly violates fundamental security principles of authentication and authorization, as it bypasses the intended security controls designed to protect system access. The impact extends beyond simple unauthorized access to include potential data breaches, system compromise, and disruption of critical network services that organizations rely upon for their infrastructure management.
Organizations affected by this vulnerability should immediately implement the recommended mitigations including applying the vendor-provided hotfixes HF2 for the affected versions, disabling anonymous BIND operations on LDAP servers, and implementing proper access controls for the REST API endpoints. Additional protective measures include enabling account lockout mechanisms, implementing rate limiting for authentication attempts, and conducting comprehensive security assessments of LDAP configurations. From a cybersecurity perspective, this vulnerability aligns with CWE-287 which addresses improper authentication issues, and maps to ATT&CK technique T1078 for valid accounts and T1566 for social engineering attacks that leverage credential guessing. The vulnerability demonstrates the importance of proper authentication flow implementation and the risks associated with overly permissive directory service configurations that can be exploited by attackers to gain unauthorized system access.