CVE-2016-4029 in WordPress
Summary
by MITRE
WordPress before 4.5 does not consider octal and hexadecimal IP address formats when determining an intranet address, which allows remote attackers to bypass an intended SSRF protection mechanism via a crafted address.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 05/08/2019
WordPress versions prior to 4.5 contained a significant security vulnerability in their IP address validation logic that enabled remote attackers to bypass intended server-side request forgery protections. This flaw existed in the core WordPress codebase where the application failed to properly sanitize and validate IP address formats when processing network requests. The vulnerability specifically impacted the way WordPress handled octal and hexadecimal representations of IP addresses during intranet address detection, creating a bypass mechanism for attackers seeking to circumvent security controls designed to prevent access to internal network resources.
The technical implementation of this vulnerability stemmed from insufficient input validation within WordPress's network request handling functionality. When WordPress processed requests containing IP addresses, it relied on a flawed algorithm that did not account for alternative numeric representations such as octal (prefixed with zero) or hexadecimal (prefixed with 0x) formats. This oversight allowed attackers to craft malicious IP addresses that would be interpreted as valid external addresses by the application's security mechanisms while actually representing internal network addresses. The vulnerability essentially created a path where an attacker could trick WordPress into making requests to internal systems that should have been blocked by default security policies.
The operational impact of CVE-2016-4029 was substantial as it enabled attackers to perform server-side request forgery attacks against WordPress installations. This vulnerability allowed remote threat actors to potentially access internal network services, databases, or other sensitive systems that were typically protected by firewall rules or network segmentation. Attackers could leverage this flaw to target internal resources such as database servers, application servers, or other network services that were not directly exposed to the internet but were accessible from the WordPress server itself. The implications extended beyond simple information disclosure, as successful exploitation could lead to complete system compromise or lateral movement within the network infrastructure.
Security researchers have classified this vulnerability under CWE-20, which represents "Improper Input Validation," and it aligns with ATT&CK techniques related to server-side request forgery and network infiltration. The vulnerability demonstrated a critical flaw in the application's trust model and input handling mechanisms, where the system failed to properly validate and normalize input data before processing. Organizations running affected WordPress versions were at significant risk of unauthorized access to their internal infrastructure, particularly in environments where WordPress installations had access to sensitive internal services. The vulnerability highlighted the importance of proper input sanitization and the need for comprehensive validation of all network-related inputs, especially when dealing with address representations that may have multiple valid formats.
The recommended mitigation strategy for this vulnerability involved upgrading to WordPress version 4.5 or later, which included the necessary code fixes to properly handle IP address validation. Additionally, organizations should implement network-level protections such as firewalls, network segmentation, and access controls to limit the potential impact of such vulnerabilities. Security teams should also conduct thorough audits of their WordPress installations to ensure no other similar validation issues exist in their custom code or third-party plugins. The vulnerability underscored the importance of maintaining up-to-date software and implementing robust security practices that consider all possible input formats and representations that attackers might exploit.