CVE-2012-0818 in RESTEasy
Summary
by MITRE
RESTEasy before 2.3.1 allows remote attackers to read arbitrary files via an external entity reference in a DOM document, aka an XML external entity (XXE) injection attack.
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Analysis
by VulDB Data Team • 12/20/2021
The vulnerability identified as CVE-2012-0818 represents a critical XML external entity injection flaw within the RESTEasy framework version 2.3.0 and earlier. This vulnerability falls under the CWE-611 weakness category, specifically addressing insecure direct object references and XML external entity processing. The flaw enables remote attackers to exploit the framework's handling of DOM documents by manipulating external entity references, creating a pathway for unauthorized file access. The vulnerability stems from inadequate input validation and sanitization within the XML parsing mechanisms of the RESTEasy web services framework, which processes incoming requests containing XML data structures.
The technical implementation of this vulnerability occurs when RESTEasy processes XML documents that contain external entity declarations. Attackers can craft malicious XML payloads that reference external entities pointing to local files on the server system. When the framework parses these documents without proper restrictions on external entity resolution, it will attempt to resolve these references, potentially exposing sensitive files such as configuration data, database credentials, or system files. The XXE injection attack leverages the fact that XML parsers typically resolve external entities by default, creating a direct access vector to the underlying file system. This vulnerability is particularly dangerous because it can be exploited through standard web service endpoints that accept XML input, making it accessible to any attacker who can send crafted requests to the affected system.
The operational impact of CVE-2012-0818 extends beyond simple file disclosure, as it can enable attackers to perform more sophisticated attacks including internal network reconnaissance, data exfiltration, and potentially system compromise. An attacker could use this vulnerability to access critical system files, application configuration, or database connection strings stored in local files. The vulnerability also presents a risk for server-side request forgery attacks, where attackers might leverage the framework's XML processing capabilities to make requests to internal services. Additionally, the flaw could facilitate denial of service conditions if attackers craft XML documents that cause the application to consume excessive resources during entity resolution. The attack vector is particularly concerning because it requires minimal privileges and can be executed through standard HTTP requests to web service endpoints, making it an attractive target for automated exploitation tools.
Mitigation strategies for CVE-2012-0818 should focus on both immediate remediation and long-term architectural improvements. The primary solution involves upgrading to RESTEasy version 2.3.1 or later, which includes proper XML parser configuration to disable external entity resolution. Organizations should also implement XML parser hardening measures such as configuring the parser to reject external entity declarations and setting up proper input validation for all XML content. Network-level protections including web application firewalls and API gateways can provide additional defense-in-depth measures to detect and block suspicious XML payloads. Security teams should conduct comprehensive vulnerability assessments to identify all instances of RESTEasy in their infrastructure and ensure proper patch management processes are in place. The remediation approach should align with NIST guidelines for XML security and incorporate principles from the MITRE ATT&CK framework, specifically addressing the initial access and privilege escalation techniques that leverage XXE vulnerabilities. Regular security testing including XML injection testing should be integrated into the development lifecycle to prevent similar vulnerabilities from emerging in future releases.