CVE-2015-3160 in Beaker
Summary
by MITRE
XML external entity (XXE) vulnerability in bkr/server/jobs.py in Beaker before 20.1 allows remote authenticated users to obtain sensitive information via submitting job XML to the server containing entity references which reference files from the Beaker server's file system.
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Analysis
by VulDB Data Team • 11/13/2019
The CVE-2015-3160 vulnerability represents a critical XML external entity processing flaw discovered in the Beaker job management system prior to version 20.1. This vulnerability resides within the bkr/server/jobs.py component and specifically affects how the system handles XML job submissions. The flaw enables remote authenticated attackers to exploit the system's XML parser by crafting malicious job XML documents containing entity references that point to sensitive files on the Beaker server's file system. This vulnerability falls under the CWE-611 category of Improper Restriction of XML External Entity Reference, which is a well-documented weakness in XML processing implementations. The attack vector requires authentication, meaning that only users with valid credentials can exploit this vulnerability, but the impact remains severe as it can expose sensitive system information.
The technical exploitation of this XXE vulnerability occurs when the Beaker server processes job XML submissions without properly validating or sanitizing external entity references. When an authenticated user submits a job XML document containing crafted entity declarations that reference local files, the XML parser resolves these entities and includes the file contents in the processing context. This allows attackers to access files that should remain protected, potentially including configuration files, database credentials, system logs, or other sensitive information stored on the server. The vulnerability demonstrates a failure in input validation and proper XML parsing security measures, as the system does not adequately restrict external entity resolution or implement proper sandboxing mechanisms for XML processing.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can provide attackers with significant insights into the Beaker server's internal structure and configuration. Attackers can potentially access sensitive files such as database connection strings, cryptographic keys, or system configuration details that could facilitate further attacks or compromise additional system components. The vulnerability also represents a potential stepping stone for more advanced attacks, as the leaked information could be used to identify other system weaknesses or to craft more sophisticated exploitation techniques. According to ATT&CK framework, this vulnerability aligns with T1083 (File and Directory Discovery) and T1566 (Phishing for Information) techniques, as it enables unauthorized file access and information gathering.
Mitigation strategies for CVE-2015-3160 should focus on implementing proper XML parsing security measures and restricting external entity resolution. Organizations should upgrade to Beaker version 20.1 or later, which includes fixes for this vulnerability. Additionally, administrators should implement XML parser configurations that disable external entity resolution entirely or restrict it to trusted sources only. The system should also enforce strict input validation on all XML job submissions, ensuring that entity declarations are either completely removed or properly sanitized before processing. Network segmentation and access controls should be implemented to limit the blast radius of potential exploitation, while regular security audits and monitoring should be conducted to detect any unauthorized access attempts. The vulnerability highlights the importance of secure coding practices and proper XML processing security, particularly in systems that handle user-submitted data that may contain structured content requiring parsing.