CVE-2018-4000 in Word Processor
Summary
by MITRE
An exploitable double-free vulnerability exists in the Office Open XML parser of Atlantis Word Processor, version 3.2.5.0. A specially crafted document can cause a TTableRow instance to be referenced twice, resulting in a double-free vulnerability when both the references go out of scope. An attacker must convince a victim to open a document in order to trigger this vulnerability.
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Analysis
by VulDB Data Team • 05/19/2023
The vulnerability identified as CVE-2018-4000 represents a critical double-free vulnerability within the Office Open XML parser implementation of Atlantis Word Processor version 3.2.5.0. This flaw resides in the document parsing logic that handles Office Open XML format files, specifically affecting how table row instances are managed during document processing. The vulnerability stems from improper memory management practices where a TTableRow object instance becomes referenced twice within the parser's memory allocation scheme, creating a scenario where the same memory location is freed twice during the document's lifecycle. This type of vulnerability falls under CWE-415, which specifically addresses double free conditions in software applications. The issue manifests when processing specially crafted Office Open XML documents that contain malformed table structures, causing the parser to maintain multiple references to the same table row object. When the document processing concludes and both references attempt to release the same memory location, the system experiences a double-free condition that can lead to memory corruption and potential code execution.
The operational impact of this vulnerability extends beyond simple memory corruption, as it creates a pathway for remote code execution when an unsuspecting user opens the malicious document. The attack vector requires social engineering to convince victims to open the crafted document, making it a typical client-side exploitation scenario. When the vulnerable parser encounters the malformed table structure, it follows the standard object lifecycle management but fails to properly track reference counts for the TTableRow instances. This results in the same memory block being deallocated twice, which can corrupt the heap memory management structures and potentially allow an attacker to manipulate the program's execution flow. The vulnerability is particularly concerning because it operates within the document parsing context, meaning legitimate office documents could be exploited if they contain specific malformed table elements or if attackers can manipulate the parsing logic through carefully constructed content. The memory corruption that occurs during the double-free process can manifest in various ways including application crashes, memory corruption, or more dangerously, arbitrary code execution.
Mitigation strategies for CVE-2018-4000 should focus on both immediate patching and defensive measures. The primary solution involves updating to a patched version of Atlantis Word Processor that corrects the memory management logic within the Office Open XML parser. Organizations should implement strict document validation policies that scan incoming Office Open XML files for malformed table structures before processing. Network-based defenses should include content filtering solutions that can detect and block suspicious Office Open XML documents with anomalous table formatting. The vulnerability demonstrates the importance of proper reference counting mechanisms in memory management, aligning with ATT&CK technique T1059.007 for execution through office applications and T1203 for exploitation through malicious documents. Administrators should consider implementing sandboxing mechanisms for document processing and establishing user awareness training to prevent successful social engineering attacks. Additionally, memory corruption vulnerabilities of this nature should be monitored through heap analysis tools and intrusion detection systems that can identify abnormal memory deallocation patterns. The remediation process should include comprehensive testing of the patched software to ensure that the memory management fixes do not introduce regressions in legitimate document processing functionality, while also validating that the fix properly handles edge cases in table structure parsing.