CVE-2023-21736 in Visio
Summary
by MITRE • 01/11/2023
Microsoft Office Visio Remote Code Execution Vulnerability. This CVE ID is unique from CVE-2023-21737, CVE-2023-21738.
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Analysis
by VulDB Data Team • 09/22/2025
Microsoft Office Visio contains a remote code execution vulnerability that arises from improper handling of specially crafted files during the rendering process. This flaw exists in the way Visio processes certain graphical elements and data structures within Visio files, creating opportunities for attackers to execute arbitrary code on affected systems. The vulnerability specifically impacts the software's ability to safely parse and render complex diagramming elements, particularly those involving embedded objects or external references. Security researchers have identified that when Visio attempts to open maliciously crafted files, the application fails to properly validate input data, leading to memory corruption that can be exploited by remote attackers.
The technical nature of this vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read errors. Attackers can leverage this weakness by crafting Visio files containing malicious payloads that trigger the vulnerable code path when the application attempts to render the diagram. The exploitation typically occurs when a user opens a specially crafted .vsdx file, which may be delivered through phishing emails, malicious websites, or compromised documents. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1203, where adversaries use malicious documents to gain initial access to target systems. The flaw affects multiple versions of Microsoft Office Visio, including various releases from 2016 through 2021, making it particularly concerning for enterprise environments where these applications are widely deployed.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with persistent access to compromised systems. Once successfully exploited, the malicious code can establish backdoors, download additional payloads, or escalate privileges to gain full system control. Organizations using Visio for diagramming and design work face significant risk, particularly in environments where users frequently open external documents or receive files from untrusted sources. The vulnerability's remote execution capability means that attackers do not need physical access to target systems, enabling widespread exploitation through email campaigns or web-based attacks. Security teams must consider the potential for lateral movement within networks once initial compromise occurs, as Visio users often work with sensitive business diagrams and may inadvertently expose confidential information.
Mitigation strategies should include immediate deployment of Microsoft's security patches and updates, which address the underlying parsing logic issues in Visio's rendering engine. Organizations should implement strict file validation policies, particularly for documents received from external sources, and consider disabling automatic opening of files from untrusted locations. Network segmentation and application whitelisting can help reduce the attack surface by preventing unauthorized execution of malicious Visio files. Security monitoring should focus on unusual Visio process activity, file access patterns, and attempts to open suspicious files. Additionally, user education programs should emphasize the dangers of opening unknown Visio files and the importance of verifying document sources before opening. Implementing email filtering solutions that can detect and block malicious Visio attachments will further reduce risk exposure. The vulnerability highlights the importance of maintaining up-to-date security patches and implementing layered defense strategies to protect against sophisticated attacks targeting productivity applications.