CVE-2018-21240 in Foxit
Summary
by MITRE
An issue was discovered in Foxit Reader and PhantomPDF before 9.2. It allows memory consumption via an ArrayBuffer(0xfffffffe) call.
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Analysis
by VulDB Data Team • 10/22/2020
The vulnerability identified as CVE-2018-21240 represents a critical memory consumption issue affecting Foxit Reader and PhantomPDF versions prior to 9.2. This flaw manifests through a specific memory allocation pattern that can be exploited to consume excessive system resources, potentially leading to denial of service conditions. The vulnerability stems from improper handling of memory allocation requests within the PDF processing engine of these applications.
The technical root cause of this vulnerability lies in the way the software processes ArrayBuffer operations, specifically when encountering an ArrayBuffer(0xfffffffe) call. This particular value represents a near-maximum integer size that, when passed to the memory allocation function, triggers unexpected behavior in the application's memory management subsystem. The flaw operates at the level of memory allocation and buffer handling, where the software fails to properly validate or constrain input parameters before proceeding with memory operations. This type of vulnerability falls under the category of improper input validation and memory management errors as classified by CWE-129 and CWE-786 respectively.
The operational impact of this vulnerability extends beyond simple resource exhaustion, as it can be leveraged by attackers to disrupt normal application functionality and potentially cause system instability. When exploited, the vulnerability allows an attacker to consume large amounts of memory through a single malicious PDF document, which could lead to application crashes, system slowdowns, or complete system hangs. The attack vector requires the victim to open a specially crafted PDF file containing the malicious ArrayBuffer call, making this a client-side exploitation scenario that aligns with ATT&CK technique T1203 for legitimate system exploitation. The vulnerability affects both Foxit Reader and PhantomPDF, indicating a widespread impact across multiple product lines from the same vendor.
Mitigation strategies for this vulnerability require immediate patching of affected software versions to 9.2 or later, where the memory allocation handling has been corrected. Organizations should implement strict PDF file validation procedures and consider deploying sandboxing solutions to isolate PDF processing activities. Network administrators should monitor for suspicious PDF file downloads and implement content filtering measures to prevent exploitation. The fix typically involves proper input validation of array buffer size parameters and implementation of memory allocation limits to prevent excessive consumption. Additionally, users should be educated about the risks of opening untrusted PDF documents and the importance of keeping software updated. Security teams should also consider implementing memory monitoring solutions to detect unusual memory consumption patterns that might indicate exploitation attempts, as this vulnerability can be used in combination with other techniques to achieve more sophisticated attacks.