CVE-2019-0540 in Office
Summary
by MITRE
A security feature bypass vulnerability exists when Microsoft Office does not validate URLs.An attacker could send a victim a specially crafted file, which could trick the victim into entering credentials, aka 'Microsoft Office Security Feature Bypass Vulnerability'.
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Analysis
by VulDB Data Team • 07/09/2023
The vulnerability described in CVE-2019-0540 represents a critical security feature bypass in Microsoft Office applications that stems from inadequate URL validation mechanisms. This weakness allows attackers to craft malicious files that can deceive users into providing sensitive authentication credentials through seemingly legitimate Office documents. The flaw exists within the application's handling of Uniform Resource Locators and demonstrates a fundamental failure in input validation that directly undermines the security model of the Office suite. Security researchers have classified this issue as a significant risk due to its potential for credential harvesting and the ease with which attackers can exploit it through social engineering techniques.
The technical implementation of this vulnerability involves Microsoft Office's insufficient validation of Uniform Resource Locators within document elements such as hyperlinks, embedded objects, or external references. When users open maliciously crafted Office files, the application fails to properly verify the legitimacy of URLs before executing or displaying content from external sources. This validation gap creates an opportunity for attackers to embed deceptive URLs that appear to lead to trusted destinations while actually redirecting users to malicious credential harvesting sites. The vulnerability specifically affects Office applications that process documents containing external references, making it particularly dangerous in enterprise environments where users frequently interact with external documents.
The operational impact of CVE-2019-0540 extends beyond simple credential theft to encompass broader security compromise potential within targeted organizations. Attackers can leverage this vulnerability to conduct sophisticated phishing campaigns where Office documents serve as the initial infection vector, leading to credential compromise and subsequent lateral movement within networks. The attack surface is particularly concerning given that Office documents are commonly shared through email, file servers, and collaboration platforms, making the exploitation vector highly accessible to threat actors. Organizations that rely heavily on Office productivity suites face significant risk of unauthorized access to sensitive systems and data repositories when this vulnerability remains unpatched.
Mitigation strategies for CVE-2019-0540 should prioritize immediate patch deployment through Microsoft's security updates, as the vulnerability requires core application modifications to address the URL validation deficiencies. Organizations should implement network-level controls such as URL filtering and content inspection systems to detect and block suspicious external references within Office documents. Security teams should also consider deploying email security solutions that can identify and quarantine documents containing potentially malicious URL patterns. Additionally, user education programs should emphasize the importance of verifying document sources and avoiding interaction with unexpected Office files from untrusted sources. According to CWE standards, this vulnerability maps to CWE-20: Improper Input Validation, while ATT&CK framework categorizes it under T1566: Phishing and T1078: Valid Accounts, highlighting both the input validation failure and the credential compromise exploitation techniques. Organizations should also consider implementing application whitelisting policies to restrict execution of Office documents from untrusted network locations and maintain comprehensive monitoring for suspicious URL access patterns.