CVE-2020-23804 in poppler
Summary
by MITRE • 08/22/2023
Uncontrolled Recursion in pdfinfo, and pdftops in poppler 0.89.0 allows remote attackers to cause a denial of service via crafted input.
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Analysis
by VulDB Data Team • 09/16/2023
The vulnerability CVE-2020-23804 represents a critical uncontrolled recursion issue affecting pdfinfo and pdftops components within the poppler PDF library version 0.89.0. This flaw resides in the handling of malformed PDF files and specifically targets the recursive parsing mechanisms used by these utilities. The vulnerability is classified under CWE-674, which deals with uncontrolled recursion, making it a significant concern for systems that process untrusted PDF content. When attackers craft malicious PDF files containing recursive structures that trigger infinite loops during parsing, the affected applications become vulnerable to denial of service attacks. The poppler library serves as a widely-used PDF rendering and manipulation toolkit in numerous operating systems and applications, including web browsers, document viewers, and server-side processing systems. This widespread adoption amplifies the potential impact of the vulnerability across multiple attack vectors and environments.
The technical implementation of this vulnerability occurs when pdfinfo and pdftops encounter PDF files with recursive structures that cause the parsing routines to enter infinite loops. These utilities are designed to extract metadata and convert PDF documents to PostScript format respectively, but they fail to implement proper recursion depth limits or termination conditions. The recursive parsing mechanism processes PDF objects and their references, and when these references create circular dependencies without proper bounds checking, the system resources become consumed indefinitely. This behavior aligns with ATT&CK technique T1499.001, which covers network denial of service attacks through resource exhaustion, and demonstrates how seemingly benign file processing can become a vector for system compromise.
The operational impact of CVE-2020-23804 extends beyond simple service disruption to potentially affect entire systems that rely on poppler for PDF processing. In web applications, email servers, and document management systems, attackers can exploit this vulnerability to exhaust system resources, causing processes to hang or crash. The vulnerability affects both local and remote attack scenarios, as any system processing untrusted PDF input becomes susceptible. Servers running automated PDF processing workflows, such as document conversion services or content management systems, face the highest risk of exploitation. The resource exhaustion typically manifests as high cpu usage, memory consumption, and process blocking, which can lead to cascading failures in dependent services. Organizations using poppler in production environments without proper input validation or resource limits face significant operational risks.
Mitigation strategies for CVE-2020-23804 require both immediate patching and operational hardening measures. The primary solution involves upgrading to poppler versions that contain fixes for the recursion handling, specifically versions released after the vulnerability disclosure. System administrators should implement input validation controls that limit the complexity of PDF files processed by applications using poppler, including setting maximum recursion depths and resource limits. Process isolation and resource monitoring become critical defensive measures, particularly for applications that must process untrusted PDF content. Implementing timeouts for PDF processing operations and establishing proper error handling for recursive structures can prevent exploitation. Organizations should also consider implementing sandboxing techniques for PDF processing and monitoring for unusual resource consumption patterns that might indicate exploitation attempts. The vulnerability underscores the importance of proper input validation and resource management in security-critical applications, aligning with security best practices outlined in NIST SP 800-160 and ISO 27001 standards for secure system design and implementation.