CVE-2019-20818 in PhantomPDF
Summary
by MITRE
An issue was discovered in Foxit Reader and PhantomPDF before 9.7. It allows memory consumption because data is created for each page of an application level.
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Analysis
by VulDB Data Team • 10/22/2020
The vulnerability identified as CVE-2019-20818 represents a memory exhaustion issue affecting Foxit Reader and PhantomPDF versions prior to 9.7. This flaw manifests when applications process documents containing multiple pages, leading to excessive memory allocation that can ultimately result in system instability or application crashes. The issue stems from how these PDF readers handle memory management during document processing, specifically when dealing with application-level data structures that are created for each individual page within a document.
From a technical perspective, this vulnerability operates as a memory leak or memory consumption flaw where the software fails to properly manage memory resources when processing multi-page documents. Each page processed by the application generates corresponding data structures that are not adequately released or managed, causing cumulative memory usage to grow exponentially with document complexity. This behavior aligns with CWE-401, which categorizes memory leaks and improper resource management as critical security concerns that can be exploited to exhaust system resources. The vulnerability is particularly concerning because it operates at the application level rather than requiring external exploitation, making it accessible through normal document processing activities.
The operational impact of CVE-2019-20818 extends beyond simple performance degradation to potentially compromise system stability and availability. When an attacker or legitimate user opens a maliciously crafted multi-page PDF document, the application consumes increasing amounts of memory until system resources are exhausted, potentially leading to application crashes, system slowdowns, or even complete system lockups. This type of vulnerability can be leveraged as a denial-of-service vector, where an attacker simply needs to provide a document with numerous pages to trigger the memory exhaustion behavior. The attack surface is broad since PDF documents are commonly shared and opened across various systems, making this vulnerability particularly dangerous in enterprise environments where PDF processing is frequent.
Security professionals should recognize this vulnerability as a potential indicator of broader resource exhaustion attack patterns that align with ATT&CK technique T1499, which covers resource exhaustion attacks targeting system resources. The recommended mitigation strategy involves immediate patching of affected Foxit Reader and PhantomPDF installations to version 9.7 or later, where the memory management issues have been addressed. Additionally, organizations should implement document validation procedures that screen incoming PDF files for suspicious page counts or structures, and consider deploying network-level protections that can detect and block potentially malicious PDF content. System administrators should also monitor memory usage patterns in environments where these applications are deployed, as unusual memory consumption can serve as an early warning indicator of exploitation attempts. The vulnerability highlights the importance of proper resource management in commercial software applications and demonstrates how seemingly benign processing operations can be exploited to create significant security impacts through resource exhaustion attacks.