CVE-2014-1756 in Office
Summary
by MITRE
Untrusted search path vulnerability in Microsoft Office 2007 SP3, 2010 SP1 and SP2, and 2013 Gold, SP1, RT, and RT SP1, when the Simplified Chinese Proofing Tool is enabled, allows local users to gain privileges via a Trojan horse DLL in the current working directory, as demonstrated by a directory that contains a .docx file, aka "Microsoft Office Chinese Grammar Checking Vulnerability."
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Analysis
by VulDB Data Team • 06/19/2021
This vulnerability represents a classic untrusted search path issue that affects multiple versions of Microsoft Office including 2007 SP3, 2010 SP1 and SP2, and 2013 Gold, SP1, RT, and RT SP1. The flaw specifically manifests when the Simplified Chinese Proofing Tool is enabled, creating a dangerous condition where the application searches for required DLL components in the current working directory before checking system directories. This behavior violates the principle of least privilege and creates an exploitable condition where malicious actors can place a specially crafted Trojan horse DLL in the same directory as a legitimate .docx file, allowing arbitrary code execution with the privileges of the user running the application.
The technical implementation of this vulnerability stems from improper DLL resolution mechanisms within Microsoft Office's Chinese grammar checking functionality. When Office processes a document with the Simplified Chinese Proofing Tool active, it attempts to load necessary linguistic libraries from the current working directory without proper validation of the source or authenticity of these components. This search path order vulnerability is classified as CWE-427 and falls under the broader category of CWE-74, which deals with improper neutralization of special elements in the context of a different component. The vulnerability essentially allows attackers to hijack the application's execution flow by placing malicious code in the search path, bypassing normal security mechanisms.
The operational impact of this vulnerability is significant as it enables local privilege escalation attacks that can be executed with minimal user interaction. An attacker needs only to place a malicious DLL in the same directory as a targeted .docx file, which could be delivered through social engineering tactics such as phishing emails or compromised shared drives. Once a user opens the document, the Office application will load the malicious DLL instead of the legitimate one, potentially allowing attackers to execute arbitrary code with the user's privileges. This vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation, making it particularly dangerous in enterprise environments where users may open documents from untrusted sources.
Mitigation strategies for this vulnerability include immediate deployment of Microsoft security updates that address the specific DLL loading behavior in the Chinese proofing tools. Organizations should also implement strict file execution policies that prevent loading of DLLs from untrusted directories and consider disabling unnecessary language proofing tools when they are not required for business operations. The principle of least privilege should be enforced by ensuring that Office applications run with minimal required permissions and that users do not have write access to directories containing Office documents. Additionally, security awareness training should emphasize the dangers of opening documents from untrusted sources and the importance of verifying document origins before execution. Network segmentation and application whitelisting solutions can further reduce the attack surface by preventing unauthorized DLL loading operations.