CVE-2018-10289 in MuPDF
Summary
by MITRE
In MuPDF 1.13.0, there is an infinite loop in the fz_skip_space function of the pdf/pdf-xref.c file. A remote adversary could leverage this vulnerability to cause a denial of service via a crafted pdf file.
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Analysis
by VulDB Data Team • 09/12/2024
The vulnerability identified as CVE-2018-10289 represents a critical denial of service flaw within the MuPDF document processing library version 1.13.0. This issue stems from an infinite loop condition that occurs within the fz_skip_space function located in the pdf/pdf-xref.c source file. The flaw manifests when processing specially crafted pdf documents that contain malformed whitespace sequences, causing the application to enter an indefinite loop during parsing operations. The vulnerability is particularly concerning as it can be exploited remotely through malicious pdf files, making it a significant threat to systems that process untrusted document content. The infinite loop consumes excessive cpu resources and effectively renders the affected system unresponsive to legitimate pdf processing requests.
The technical implementation of this vulnerability involves the improper handling of whitespace characters within pdf cross-reference tables during document parsing. When the fz_skip_space function encounters malformed or intentionally crafted whitespace sequences in the pdf file structure, it fails to properly terminate its loop execution. This function is responsible for skipping over whitespace characters while parsing pdf objects and cross-reference entries, but the lack of proper bounds checking or termination conditions allows the loop to continue indefinitely. The flaw demonstrates a classic example of inadequate input validation and error handling within document parsing routines, which is categorized under CWE-835 in the Common Weakness Enumeration catalog. The vulnerability is particularly dangerous because it can be triggered without requiring any special privileges or authentication, making it accessible to remote attackers who can simply send a malicious pdf file to exploit the issue.
The operational impact of CVE-2018-10289 extends beyond simple service disruption, as it can lead to complete system resource exhaustion and application unavailability. Systems that rely on MuPDF for pdf processing, including web applications, document management systems, and email servers, become vulnerable to sustained denial of service attacks. Attackers can repeatedly submit malicious pdf files to exhaust system resources, potentially causing cascading failures in environments where multiple pdf processing threads or processes are running simultaneously. The vulnerability affects the fundamental document parsing capabilities of applications using MuPDF, leading to potential data loss, service interruptions, and increased operational costs due to system maintenance and recovery efforts. This type of vulnerability aligns with ATT&CK technique T1499.004, which involves network denial of service attacks through resource exhaustion, and represents a significant threat to availability in information security triads.
Mitigation strategies for CVE-2018-10289 should prioritize immediate patching of affected systems with updated MuPDF versions that contain the necessary code fixes. Organizations should implement comprehensive input validation measures that include timeout mechanisms and resource limits when processing pdf documents, preventing infinite loops from consuming excessive system resources. Network-based defenses can include pdf file content filtering and sandboxing mechanisms that isolate pdf processing operations from critical system components. Additionally, security teams should establish monitoring procedures to detect unusual cpu usage patterns that may indicate exploitation attempts. The vulnerability underscores the importance of regular security updates and vulnerability management processes, as it represents a preventable issue that was addressed in subsequent releases of the MuPDF library. System administrators should also consider implementing application whitelisting and access controls to limit pdf processing capabilities to trusted sources, reducing the attack surface available to potential exploiters.