CVE-2018-3843 in Foxit
Summary
by MITRE
An exploitable type confusion vulnerability exists in the way Foxit PDF Reader version 9.0.1.1049 parses files with associated file annotations. A specially crafted PDF document can lead to an object of invalid type to be dereferenced, which can potentially lead to sensitive memory disclosure, and possibly to arbitrary code execution. An attacker needs to trick the user into opening the malicious file to trigger this vulnerability. If the browser plugin extension is enabled, visiting a malicious site can also trigger the vulnerability.
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Analysis
by VulDB Data Team • 03/03/2023
The vulnerability identified as CVE-2018-3843 represents a critical type confusion flaw in Foxit PDF Reader version 9.0.1.1049 that specifically manifests during the parsing of PDF files containing associated file annotations. This type confusion vulnerability stems from improper handling of object types within the document processing pipeline, where the software fails to properly validate or distinguish between different data types during the parsing process. The flaw is categorized under CWE-476 as a NULL pointer dereference that occurs due to incorrect type handling, which is a common vector for exploitation in PDF rendering engines. The vulnerability's exploitation requires a malicious PDF file that manipulates the structure of associated file annotations to force the application into dereferencing an object of an unexpected type.
The technical implementation of this vulnerability occurs when the Foxit PDF Reader encounters a specially crafted PDF document that contains malformed associated file annotation data. During the parsing phase, the application's object management system fails to properly validate the type of objects being processed, leading to a situation where a pointer intended to reference one type of object may inadvertently point to memory containing data of a different type. This misalignment between expected and actual object types creates a condition where the application attempts to access memory locations containing invalid or unexpected data structures, resulting in potential memory disclosure and execution flow manipulation. The vulnerability specifically affects the handling of file attachment annotations where the software does not properly validate the object type before performing operations on the associated data structures.
The operational impact of CVE-2018-3843 extends beyond simple memory corruption, as it provides potential attackers with pathways for privilege escalation and arbitrary code execution. When successfully exploited, the vulnerability can lead to sensitive memory disclosure that may reveal critical information such as stack pointers, heap addresses, or other application state data that could be leveraged in subsequent attacks. The attack vector requires user interaction through opening a malicious PDF file, making it particularly dangerous in phishing scenarios or when users are tricked into visiting compromised websites that deliver malicious PDF content through browser plugins. This vulnerability particularly impacts enterprise environments where PDF documents are frequently shared and opened, and where the browser plugin extension may be enabled, expanding the attack surface to include web-based delivery mechanisms.
Mitigation strategies for CVE-2018-3843 should focus on immediate software updates to versions that have patched the type confusion handling, as well as implementing defensive measures such as restricting PDF file execution in web browsers and disabling the browser plugin extension when not required. Organizations should also consider implementing application whitelisting policies that restrict execution of PDF readers to trusted versions and monitor for unusual PDF processing activities. The vulnerability aligns with ATT&CK technique T1203 as it enables execution through legitimate system processes, and represents a classic example of how PDF rendering engines can be exploited through manipulation of document structures. Security teams should also implement network-based intrusion detection systems that can identify and block known malicious PDF patterns, and conduct regular security assessments to ensure that all PDF processing components are updated to the latest secure versions.