CVE-2019-17063 in PDFxStream
Summary
by MITRE
In Snowtide PDFxStream before 3.7.1 (for Java), a crafted PDF file can trigger an extremely long running computation because of page-tree mishandling.
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Analysis
by VulDB Data Team • 12/29/2023
CVE-2019-17063 represents a critical denial of service vulnerability affecting Snowtide PDFxStream versions prior to 3.7.1 in Java environments. This vulnerability stems from improper handling of the PDF page tree structure during document parsing operations, creating a condition where maliciously crafted PDF files can induce computationally intensive processing sequences that dramatically extend execution time. The flaw manifests when the PDF parser encounters specific page tree configurations that cause it to enter recursive or iterative processing loops, leading to excessive CPU utilization and potential system resource exhaustion.
The technical implementation of this vulnerability involves the PDF parser's failure to properly validate and sanitize the page tree hierarchy present in PDF documents. When processing a malformed PDF with crafted page tree references, the parsing logic attempts to traverse and resolve page references in a manner that creates exponential computational complexity. This behavior aligns with CWE-400, which categorizes issues related to excessive resource consumption through uncontrolled resource consumption, and specifically demonstrates the dangers of inadequate input validation in parsing libraries. The vulnerability exploits the fundamental assumption that page tree structures in valid PDF documents follow predictable hierarchical patterns, but maliciously constructed documents can subvert these expectations through circular references or deeply nested structures.
From an operational perspective, this vulnerability presents significant risks to systems that process untrusted PDF content, particularly those serving as document ingestion points for content management systems, email gateways, or document conversion services. The impact extends beyond simple service disruption to potentially enable resource exhaustion attacks that can degrade system performance or cause complete service unavailability. Attackers can craft PDF files that, when processed by vulnerable systems, consume excessive CPU cycles and memory resources, effectively creating a denial of service condition. This vulnerability particularly affects environments where automated PDF processing occurs without proper resource limits or timeout mechanisms, making it a prime target for abuse in distributed denial of service scenarios or resource exhaustion attacks.
The recommended mitigation strategy involves upgrading to Snowtide PDFxStream version 3.7.1 or later, which implements proper bounds checking and resource management for page tree processing. Organizations should also implement additional protective measures including setting strict timeouts for PDF processing operations, implementing resource quotas for parsing tasks, and deploying input validation mechanisms that sanitize PDF content before processing. Security practitioners should consider implementing monitoring for unusual CPU usage patterns during PDF processing and establish automated alerting for extended processing times that may indicate exploitation attempts. The vulnerability demonstrates the importance of implementing robust input validation and resource management in parsing libraries, as outlined in the ATT&CK framework's mitigation strategies for resource exhaustion attacks. Additionally, organizations should conduct regular security assessments of their PDF processing pipelines to identify and remediate similar vulnerabilities in other third-party libraries that may be susceptible to similar issues.