CVE-2021-41110 in cwlviewer
Summary
by MITRE • 10/01/2021
cwlviewer is a web application to view and share Common Workflow Language workflows. Versions prior to 1.3.1 contain a Deserialization of Untrusted Data vulnerability. Commit number f6066f09edb70033a2ce80200e9fa9e70a5c29de (dated 2021-09-30) contains a patch. There are no available workarounds aside from installing the patch. The SnakeYaml constructor, by default, allows any data to be parsed. To fix the issue the object needs to be created with a `SafeConstructor` object, as seen in the patch.
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Analysis
by VulDB Data Team • 10/08/2021
The CVE-2021-41110 vulnerability affects cwlviewer, a web application designed for viewing and sharing Common Workflow Language workflows. This application serves as a critical tool in computational biology and bioinformatics environments where researchers need to visualize and share complex workflow structures. The vulnerability stems from improper handling of untrusted data during the deserialization process, creating a significant security risk for systems that rely on this workflow visualization tool. The flaw specifically impacts versions prior to 1.3.1, making all earlier releases susceptible to exploitation by malicious actors who can manipulate the application's data parsing mechanisms.
The technical root cause of this vulnerability lies in the application's use of the SnakeYaml library for parsing YAML data structures. By default, SnakeYaml's constructor allows any data to be parsed without proper validation, creating an attack surface where maliciously crafted input can trigger unintended object instantiation. This deserialization flaw enables remote code execution when untrusted YAML data is processed through the vulnerable application. The vulnerability maps directly to CWE-502, which describes Deserialization of Untrusted Data, a well-known weakness that has been exploited in numerous high-profile security incidents. The issue represents a classic case where insufficient input validation during the deserialization process creates a pathway for arbitrary code execution.
The operational impact of CVE-2021-41110 extends beyond simple data corruption or application instability. In environments where cwlviewer is used to manage complex computational workflows, exploitation could allow attackers to execute arbitrary code on affected systems, potentially leading to complete system compromise. This vulnerability is particularly concerning in research environments where sensitive data and proprietary workflows are processed, as attackers could gain access to confidential computational resources. The vulnerability affects the core functionality of the application, making it impossible to safely process any YAML input without risking system compromise. Organizations using cwlviewer in production environments face significant risk of data breaches, system infiltration, and potential disruption of critical computational workflows.
The fix for this vulnerability requires implementing a safe constructor approach when processing YAML data. The patch referenced in commit f6066f09edb70033a2ce80200e9fa9e70a5c29de demonstrates the proper solution by replacing the default constructor with a SafeConstructor object. This change ensures that only trusted data types can be instantiated during the YAML parsing process, effectively preventing malicious code execution. The recommended mitigation strategy involves immediate deployment of version 1.3.1 or later, as no viable workarounds exist for the vulnerability. Organizations should also consider implementing network segmentation and monitoring for suspicious YAML processing activities as additional defensive measures. The vulnerability highlights the critical importance of secure coding practices in applications that process external data, particularly in environments where computational workflows involve sensitive research data and complex processing pipelines. This issue aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter, as exploitation could enable attackers to execute arbitrary commands through the deserialization vulnerability, potentially leading to full system compromise and data exfiltration.