CVE-2019-10782 in Checkstyle
Summary
by MITRE
All versions of com.puppycrawl.tools:checkstyle before 8.29 are vulnerable to XML External Entity (XXE) Injection due to an incomplete fix for CVE-2019-9658.
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Analysis
by VulDB Data Team • 03/27/2024
The vulnerability identified as CVE-2019-10782 affects the checkstyle library version 8.29 and earlier, representing a critical XML External Entity injection flaw that stems from an inadequate remediation of a previous vulnerability. This issue resides within the com.puppycrawl.tools:checkstyle artifact, which is widely utilized for enforcing coding standards and validating java source code against predefined style guides across development environments. The flaw manifests when the tool processes XML configuration files, particularly those containing external entity references that can be exploited by malicious actors to access local resources or perform server-side request forgery attacks. The incomplete fix for CVE-2019-9658 specifically failed to address all potential XXE attack vectors within the library's XML parsing mechanisms, leaving the system exposed to unauthorized data access and potential system compromise.
The technical implementation of this vulnerability occurs through the library's XML processing capabilities where it fails to properly disable external entity resolution when parsing configuration files. When checkstyle encounters XML documents containing external entity declarations, it does not adequately restrict the parser from resolving these references against external resources, thereby allowing attackers to craft malicious XML payloads that can trigger unauthorized access to local files, network resources, or even internal services. This flaw operates at the parser level and affects the core functionality of the tool when processing user-provided or third-party configuration files that might contain crafted XXE payloads, making it particularly dangerous in environments where untrusted XML content is processed.
The operational impact of this vulnerability extends beyond simple code validation, as it creates a potential attack surface that could be exploited in continuous integration pipelines, automated build systems, and development environments where checkstyle is integrated. Attackers could leverage this weakness to extract sensitive information from the build servers, access internal network resources, or perform reconnaissance activities by reading local files that contain credentials, configuration data, or other sensitive information. The vulnerability is particularly concerning in enterprise environments where checkstyle is used extensively across multiple projects and development teams, as a single compromised configuration file could potentially lead to widespread information disclosure across the organization. This issue also aligns with ATT&CK technique T1566.001 for initial access through malicious files and T1083 for file and directory discovery.
Organizations should immediately upgrade to checkstyle version 8.29 or later, which contains the complete fix for this XXE vulnerability. The remediation involves proper disabling of external entity resolution and normalization of XML parsing behavior to prevent any unauthorized resource access. Security teams should also implement network segmentation and monitoring to detect potential exploitation attempts, particularly when checkstyle processes configuration files from untrusted sources. Additionally, organizations should conduct thorough audits of their existing checkstyle configurations to ensure no external entity references are being processed in production environments. The vulnerability demonstrates the importance of comprehensive security testing and proper validation of security patches, as incomplete fixes can leave systems vulnerable to the same class of attacks. This issue also highlights the need for robust input validation and secure coding practices in XML processing libraries, aligning with CWE-611 for improper restriction of XML external entity reference and CWE-829 for inclusion of functionality from untrusted source.