CVE-2018-8036 in PDFbox
Summary
by MITRE
In Apache PDFBox 1.8.0 to 1.8.14 and 2.0.0RC1 to 2.0.10, a carefully crafted (or fuzzed) file can trigger an infinite loop which leads to an out of memory exception in Apache PDFBox's AFMParser.
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Analysis
by VulDB Data Team • 04/03/2023
The vulnerability identified as CVE-2018-8036 represents a critical denial of service weakness within Apache PDFBox, a widely used Java library for processing pdf documents. This flaw affects versions ranging from 1.8.0 through 1.8.14 and 2.0.0RC1 through 2.0.10, making it a significant concern for organizations relying on this library for pdf document handling. The vulnerability stems from improper input validation within the AFMParser component, which is responsible for parsing Adobe Font Metrics files that are commonly embedded within pdf documents. When processing maliciously crafted pdf files, the parser enters an infinite loop that consumes excessive system resources leading to memory exhaustion and application crashes.
The technical nature of this vulnerability aligns with CWE-835, which describes the weakness of an infinite loop or infinite recursion in software systems. The flaw occurs specifically within the AFMParser class where malformed input data triggers a condition that causes the parser to repeatedly process the same data without proper termination conditions. This type of vulnerability is particularly dangerous because it can be exploited through simple pdf file manipulation without requiring complex attack vectors or privileged access. The infinite loop manifests as a resource exhaustion attack that can be executed remotely through any application or service that utilizes Apache PDFBox for pdf processing. Attackers can craft pdf files containing specially designed AFM data structures that cause the parser to enter an endless processing cycle, consuming cpu cycles and memory resources until the system becomes unresponsive or crashes entirely.
The operational impact of CVE-2018-8036 extends beyond simple application crashes to encompass broader system stability and availability concerns. Organizations using Apache PDFBox in web applications, document processing services, or automated workflows face significant risk of service disruption when this vulnerability is exploited. The vulnerability can be leveraged in distributed denial of service scenarios where multiple malicious pdf files are processed simultaneously, amplifying the resource consumption effects. Systems that process untrusted pdf documents, such as email servers, document management platforms, or content management systems, become particularly vulnerable. The memory exhaustion aspect of this vulnerability means that even small malicious pdf files can cause substantial system resource consumption, potentially leading to cascading failures in larger applications or cloud environments where resource limits are strictly enforced.
Mitigation strategies for CVE-2018-8036 primarily focus on immediate version upgrades to patched releases of Apache PDFBox, specifically versions 1.8.15 and 2.0.11 or later. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing affected versions of the library and prioritize patching efforts accordingly. Additional defensive measures include implementing input validation and sanitization layers before pdf processing, establishing resource limits and timeouts for document parsing operations, and deploying monitoring systems to detect unusual resource consumption patterns. The vulnerability demonstrates the importance of proper input validation and termination condition implementation in parsing libraries, aligning with ATT&CK technique T1499.004 for resource exhaustion attacks. Network segmentation and application whitelisting can provide additional defense in depth, limiting the potential impact of successful exploitation attempts. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other parsing components and ensure comprehensive protection against similar attack vectors.