CVE-2015-8021 in BIG-IP
Summary
by MITRE
Incomplete blacklist vulnerability in the Configuration utility in F5 BIG-IP LTM, Analytics, APM, ASM, GTM, Link Controller, and PSM 11.x before 11.2.1 HF11, 11.3.x, 11.4.0 before HF8, and 11.4.1 before HF6; BIG-IP AAM 11.4.0 before HF8 and 11.4.1 before HF6; BIG-IP AFM and PEM 11.3.x, 11.4.0 before HF8, and 11.4.1 before HF6; and BIG-IP Edge Gateway, WebAccelerator, and WOM 11.x before 11.2.1 HF11 and 11.3.0 allows remote authenticated users to upload files via uploadImage.php.
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Analysis
by VulDB Data Team • 07/13/2022
The CVE-2015-8021 vulnerability represents a critical incomplete blacklist security flaw within the F5 BIG-IP product suite, affecting multiple modules including Local Traffic Manager Analytics APM ASM GTM Link Controller and PSM across various version ranges. This vulnerability specifically targets the Configuration utility's file upload functionality through the uploadImage.php endpoint, creating a significant attack surface for remote authenticated adversaries. The issue stems from insufficient validation mechanisms that fail to properly filter or reject potentially malicious file types, allowing attackers to bypass intended security controls. The affected systems include F5 BIG-IP versions 11.x before specific hotfixes, with particular attention to versions 11.2.1 HF11 11.3.x 11.4.0 before HF8 and 11.4.1 before HF6 across multiple product lines. This vulnerability aligns with CWE-20 Improper Input Validation and falls under the ATT&CK technique T1190 Exploit Public-Facing Application, representing a classic path to arbitrary code execution through file upload mechanisms.
The technical implementation of this vulnerability exploits the inadequacy of the blacklist validation approach used by the F5 BIG-IP systems. Rather than implementing robust whitelist-based validation or comprehensive file type checking, the system relies on an incomplete blacklist that fails to account for all potentially dangerous file extensions or MIME types. Attackers can leverage this weakness by uploading files with extensions that are not properly blacklisted, such as .php .asp .jsp or other server-side include formats that could execute code on the target system. The uploadImage.php script serves as the primary vector, where authenticated users can submit files without proper sanitization, potentially leading to remote code execution. This vulnerability represents a fundamental flaw in input validation design patterns and demonstrates the inherent risks of relying solely on blacklist approaches for security controls. The impact is amplified by the fact that the vulnerability affects multiple F5 modules, increasing the attack surface and potential exploitation scenarios.
The operational impact of CVE-2015-8021 extends beyond simple file upload capabilities and can result in complete system compromise when exploited successfully. Remote authenticated attackers with valid credentials can leverage this vulnerability to execute arbitrary code on the affected BIG-IP systems, potentially leading to data exfiltration, system infiltration, or complete service disruption. The vulnerability's presence across multiple F5 modules including AAM AFM PEM Edge Gateway WebAccelerator and WOM systems creates a widespread risk profile that affects organizations relying on F5 load balancing and application delivery solutions. Organizations may experience unauthorized access to sensitive network infrastructure, potential lateral movement within their network, and significant operational disruption. The vulnerability's ability to bypass existing security controls through a simple file upload mechanism makes it particularly dangerous as it can be exploited without requiring extensive privileges or complex attack chains.
Mitigation strategies for CVE-2015-8021 should focus on immediate patching of affected F5 BIG-IP systems with the appropriate hotfixes, specifically targeting the versions mentioned in the vulnerability description including 11.2.1 HF11 11.3.x 11.4.0 before HF8 and 11.4.1 before HF6. Organizations should implement comprehensive file validation policies that move away from incomplete blacklist approaches toward robust whitelist validation, ensuring that only explicitly permitted file types are accepted. Network segmentation and access control measures should be enforced to limit the scope of potential exploitation, particularly restricting access to the uploadImage.php endpoint. Security monitoring should be enhanced to detect unusual file upload activities and unauthorized access attempts. The implementation of web application firewalls and additional input validation controls can provide layered defense against similar vulnerabilities. Organizations should also conduct thorough vulnerability assessments across their F5 infrastructure to identify any additional instances of incomplete blacklist implementations that may present similar risks, ensuring that all affected systems receive appropriate remediation measures.