CVE-2017-7515 in Poppler
Summary
by MITRE
poppler through version 0.55.0 is vulnerable to an uncontrolled recursion in pdfunite resulting into potential denial-of-service.
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Analysis
by VulDB Data Team • 12/08/2022
The vulnerability identified as CVE-2017-7515 affects the poppler PDF library version 0.55.0 and earlier, specifically within the pdfunite utility which is designed to concatenate multiple PDF files into a single document. This flaw represents a classic example of uncontrolled recursion that can lead to denial-of-service conditions when processing specially crafted PDF files. The issue manifests when the pdfunite tool encounters malformed PDF structures that trigger recursive processing without proper termination conditions, allowing an attacker to craft malicious input that causes the application to enter infinite recursive loops.
The technical implementation of this vulnerability stems from insufficient input validation and lack of recursion depth limits within the PDF parsing logic of pdfunite. When processing PDF files containing nested objects or circular references that exceed normal structural boundaries, the utility fails to implement proper recursion guards or stack depth monitoring. This type of flaw maps directly to CWE-674, which describes "Uncontrolled Recursion" and falls under the broader category of software vulnerabilities that can cause system resource exhaustion through iterative processing. The vulnerability is particularly concerning because it can be exploited through simple file manipulation without requiring complex attack vectors or user interaction.
From an operational perspective, this vulnerability poses significant risks to systems that rely on pdfunite for PDF processing tasks, particularly in environments where untrusted PDF files are processed automatically. The denial-of-service impact can be severe as the recursive behavior consumes system resources including memory and cpu cycles, potentially leading to complete system instability or service unavailability. Attackers can exploit this vulnerability by preparing malicious PDF files that contain recursive structures designed to trigger the uncontrolled recursion in pdfunite, effectively creating a resource exhaustion attack that can be executed with minimal technical expertise. The vulnerability affects not only individual systems but also broader service availability when the utility is part of automated workflows or web applications processing PDF documents.
Organizations should implement immediate mitigations including updating to poppler version 0.56.0 or later where this vulnerability has been addressed through proper recursion depth limiting and enhanced input validation. System administrators should also consider implementing additional protections such as resource limits on pdfunite processes, input sanitization for PDF files before processing, and monitoring for abnormal resource consumption patterns. The ATT&CK framework categorizes this type of vulnerability under T1499.004 which describes "Endpoint Denial of Service" and represents a common attack pattern where adversaries leverage software flaws to exhaust system resources. Additionally, implementing proper input validation and recursion monitoring mechanisms aligns with security best practices outlined in NIST SP 800-53 and ISO 27001 frameworks, emphasizing the importance of robust software design and defensive programming techniques to prevent such resource exhaustion attacks.