CVE-2021-32754 in FlowDroid
Summary
by MITRE • 07/13/2021
FlowDroid is a data flow analysis tool. FlowDroid versions prior to 2.9.0 contained an XML external entity (XXE) vulnerability that allowed an attacker who had control over the source/sink definition file in XML format to read files from external locations. In order for this to occur, the XML-based format for sources and sinks had to be used and the attacker had to able control the source/sink definition file. The vulnerability was patched in version 2.9.0. As a workaround, do not allow untrusted entities to control the source/sink definition file.
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Analysis
by VulDB Data Team • 07/15/2021
FlowDroid represents a critical data flow analysis tool widely utilized in cybersecurity for identifying potential security vulnerabilities within applications through automated analysis of data flows. The vulnerability identified as CVE-2021-32754 manifests as an XML external entity processing flaw that specifically impacts versions prior to 2.9.0, creating a significant attack surface for malicious actors seeking to exploit the tool's configuration mechanisms. This vulnerability falls under the CWE-611 category of XML External Entity Processing, which is classified as a serious weakness in software applications that process XML data without proper validation and sanitization. The flaw specifically affects the source and sink definition file processing functionality, where FlowDroid accepts XML-formatted configuration files that define the points of data entry and exit within analyzed applications.
The technical exploitation of this vulnerability requires an attacker to gain control over the source/sink definition files, which are typically XML-based configuration components used by FlowDroid to understand how data moves through applications. When FlowDroid processes these XML files, it fails to properly validate or sanitize external entity references, allowing attackers to craft malicious XML content that can trigger unintended file system access. The vulnerability operates through the standard XXE attack pattern where an attacker can construct XML content that references external resources, potentially enabling them to read arbitrary files from the system where FlowDroid is running. This represents a privilege escalation scenario where an attacker with control over configuration files can leverage the tool's legitimate file reading capabilities to access sensitive information that should remain protected.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to access configuration files, credentials, or other sensitive data stored on the system where FlowDroid operates. In enterprise environments where FlowDroid is used for security analysis of applications, this vulnerability could allow attackers to extract sensitive information from the analysis infrastructure itself, potentially compromising the security posture of the entire organization. The vulnerability's exploitation requires specific conditions to be met, including the attacker's ability to control the XML-based source/sink definition files, but once achieved, it provides a direct path to unauthorized file system access. This makes the vulnerability particularly concerning in environments where multiple parties may have access to configuration files or where automated processes might inadvertently expose these files to untrusted users.
Organizations utilizing FlowDroid should immediately upgrade to version 2.9.0 or later to remediate this vulnerability, as the patch addresses the core XXE processing issue by implementing proper XML validation and entity handling. The recommended workaround of preventing untrusted entities from controlling source/sink definition files aligns with fundamental security principles of least privilege and access control, ensuring that only authorized personnel can modify critical configuration components. Security practitioners should also implement additional monitoring and access controls around the directories containing FlowDroid configuration files, as this vulnerability demonstrates how legitimate security tools can become attack vectors when not properly secured. The ATT&CK framework categorizes this type of vulnerability under T1552.001 - Unsecured Credentials, as it represents an attack vector that can be used to access sensitive information through improperly secured configuration mechanisms. Organizations should also consider implementing network segmentation and access controls to limit where FlowDroid can be deployed and how it can access system resources, reducing the potential impact of similar vulnerabilities in other components of their security infrastructure.