CVE-2018-11797 in Retail Xstore Point of Service
Summary
by MITRE
In Apache PDFBox 1.8.0 to 1.8.15 and 2.0.0RC1 to 2.0.11, a carefully crafted PDF file can trigger an extremely long running computation when parsing the page tree.
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Analysis
by VulDB Data Team • 05/07/2025
Apache PDFBox vulnerability CVE-2018-11797 represents a significant denial of service threat that affects versions ranging from 1.8.0 through 1.8.15 and 2.0.0RC1 through 2.0.11. This flaw manifests when processing specifically crafted PDF documents that contain malformed page tree structures, leading to excessive computational overhead during parsing operations. The vulnerability stems from inadequate input validation and insufficient recursion depth controls within the PDF parsing logic, allowing malicious actors to construct PDF files that cause the parser to enter infinite or extremely prolonged computational loops when traversing the page tree hierarchy.
The technical implementation of this vulnerability resides in the page tree parsing mechanism where PDFBox fails to properly validate the structural integrity of page tree nodes and their relationships. When encountering malformed or recursively structured page tree entries, the parser's traversal algorithm continues processing without adequate bounds checking, resulting in computational complexity that grows exponentially with the malicious input structure. This behavior directly maps to CWE-835, which describes the weakness of infinite loops in software systems, and demonstrates how improper input validation can lead to resource exhaustion attacks. The vulnerability operates at the parsing layer of the PDF processing pipeline, making it particularly dangerous as it can affect any application utilizing affected PDFBox versions for document processing.
The operational impact of CVE-2018-11797 extends beyond simple service disruption, as it can be leveraged in various attack scenarios including resource exhaustion attacks against web applications, email servers, and document processing systems. When exploited, the vulnerability causes significant CPU utilization spikes and can lead to complete system unresponsiveness or application crashes, particularly affecting systems with limited computational resources. This makes it especially dangerous in cloud environments where resource contention can amplify the effects of such denial of service conditions. The vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion, and represents a classic example of how parsing vulnerabilities can be weaponized to consume system resources without requiring elevated privileges or complex exploitation techniques.
Mitigation strategies for this vulnerability focus primarily on upgrading to patched versions of Apache PDFBox, specifically versions 1.8.16 and 2.0.12 or later, which include proper bounds checking and recursion limiting mechanisms in the page tree parsing logic. Organizations should implement input validation measures that restrict the complexity of PDF documents processed by systems using PDFBox, including setting maximum limits on page tree depth and node counts. Additionally, deploying defensive measures such as resource monitoring and automated alerting systems can help detect unusual processing patterns that may indicate exploitation attempts. Network-level protections including PDF file scanning and content filtering can provide additional layers of defense, while application-level sandboxing of PDF processing functions can limit the potential impact should the vulnerability be successfully exploited in the wild.