CVE-2016-5002 in Archiva
Summary
by MITRE
XML external entity (XXE) vulnerability in the Apache XML-RPC (aka ws-xmlrpc) library 3.1.3, as used in Apache Archiva, allows remote attackers to conduct server-side request forgery (SSRF) attacks via a crafted DTD.
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Analysis
by VulDB Data Team • 09/09/2022
The CVE-2016-5002 vulnerability represents a critical XML external entity injection flaw within the Apache XML-RPC library version 3.1.3, which was subsequently exploited in Apache Archiva applications. This vulnerability stems from insufficient input validation and improper handling of external entity references within XML parsing operations. The flaw enables malicious actors to manipulate XML processing behavior by introducing external entities that can reference remote resources or internal system components, fundamentally compromising the security posture of affected systems.
The technical implementation of this vulnerability occurs when the XML-RPC library processes incoming XML requests without adequate restrictions on external entity resolution. Attackers can craft specially formatted DTD (Document Type Definition) declarations that reference external resources through protocols such as http, https, ftp, or file access. When the vulnerable library parses these requests, it automatically resolves the external entities, potentially leading to unauthorized data exfiltration, internal network reconnaissance, or server-side request forgery attacks. The vulnerability specifically targets the XML parsing mechanisms within the ws-xmlrpc library, which is commonly integrated into various enterprise applications including Apache Archiva for repository management.
The operational impact of CVE-2016-5002 extends beyond simple data theft, as it enables sophisticated attack vectors that can bypass traditional network security controls. Remote attackers can leverage this vulnerability to perform server-side request forgery by making requests to internal services that would normally be restricted by firewalls or network segmentation. This capability allows attackers to probe internal networks, access sensitive data stored on internal servers, or even escalate privileges through the exploitation of other vulnerabilities discovered during the reconnaissance phase. The vulnerability is particularly dangerous in enterprise environments where Archiva is used for managing critical software artifacts and repository data, as it can lead to complete compromise of the affected systems.
Organizations should implement multiple layers of defense to mitigate the risks associated with CVE-2016-5002. The primary recommendation involves upgrading to patched versions of the Apache XML-RPC library where external entity resolution has been properly restricted or disabled. System administrators should also configure XML parsers to disable external entity resolution entirely, particularly when processing untrusted input from network sources. Network segmentation and firewall rules should be enforced to limit access to internal services that might be targeted through SSRF attacks. Additionally, implementing proper input validation and sanitization mechanisms for all XML processing components can provide defense-in-depth protection. This vulnerability aligns with CWE-611 (Improper Restriction of XML External Entity Reference) and represents a common attack pattern documented in the MITRE ATT&CK framework under T1190 (Exploit Public-Facing Application) and T1071.5 (Application Layer Protocol: XML). Organizations must also consider implementing network monitoring solutions to detect anomalous outbound requests that may indicate exploitation attempts, as the vulnerability can be used to establish covert communication channels with attacker-controlled external resources.