CVE-2020-1335 in Excel
Summary
by MITRE
<p>A remote code execution vulnerability exists in Microsoft Excel software when the software fails to properly handle objects in memory. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the current user. If the current user is logged on with administrative user rights, an attacker could take control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.</p> <p>Exploitation of the vulnerability requires that a user open a specially crafted file with an affected version of Microsoft Excel. In an email attack scenario, an attacker could exploit the vulnerability by sending the specially crafted file to the user and convincing the user to open the file. In a web-based attack scenario, an attacker could host a website (or leverage a compromised website that accepts or hosts user-provided content) containing a specially crafted file designed to exploit the vulnerability. An attacker would have no way to force users to visit the website. Instead, an attacker would have to convince users to click a link, typically by way of an enticement in an email or instant message, and then convince them to open the specially crafted file.</p> <p>The security update addresses the vulnerability by correcting how Microsoft Excel handles objects in memory.</p>
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Analysis
by VulDB Data Team • 02/24/2026
The vulnerability identified as CVE-2020-1335 represents a critical remote code execution flaw in Microsoft Excel software that stems from improper handling of memory objects during file processing operations. This weakness creates a pathway for attackers to execute arbitrary code within the context of the current user's privileges, potentially leading to complete system compromise when the target user operates with administrative rights. The vulnerability manifests when Excel encounters specially crafted file content that triggers memory corruption during object processing, allowing malicious actors to exploit this memory handling flaw to gain unauthorized system access.
The attack vector for CVE-2020-1335 requires user interaction through opening a malicious file, making it particularly dangerous in social engineering scenarios. The exploitation process begins with an attacker crafting a file designed to trigger the memory handling vulnerability within Excel's processing engine. This crafted file could be delivered through email attachments in phishing campaigns or hosted on compromised websites that entice users to download and open the malicious content. The attack chain relies on user trust and behavior modification, as users must be convinced to open the file despite security warnings or suspicious content indicators. The vulnerability does not allow automatic exploitation without user interaction, but this requirement does not diminish its threat level given the common success rates of social engineering attacks.
From a technical perspective, the flaw falls under the category of memory corruption vulnerabilities that can lead to arbitrary code execution, specifically aligning with CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write operations. The vulnerability demonstrates characteristics consistent with heap-based buffer overflow conditions where Excel's memory management fails to properly validate object boundaries during file parsing operations. This type of vulnerability is particularly dangerous because it allows attackers to overwrite memory locations with malicious code, potentially redirecting program execution flow to execute attacker-controlled instructions. The memory handling defect occurs during the parsing of structured file formats where Excel processes embedded objects, charts, or other complex data elements that require memory allocation and management.
The operational impact of CVE-2020-1335 extends beyond simple code execution to potentially enable full system compromise when exploited against administrative accounts. Successful exploitation allows attackers to install programs, modify or delete data, and create new accounts with elevated privileges, effectively granting complete control over the compromised system. Organizations with users operating under administrative privileges face the highest risk, as these accounts provide unrestricted access to system resources and data. Users with standard accounts may experience limited impact, though they can still be targeted for privilege escalation attacks or used as stepping stones for broader network compromise. The vulnerability affects multiple versions of Microsoft Excel across different operating systems, making it a widespread concern for enterprise environments that rely on spreadsheet processing applications.
Security mitigation for CVE-2020-1335 primarily involves applying the official Microsoft security update that addresses the memory handling flaw in Excel's object processing routines. Organizations should implement comprehensive patch management policies that ensure all systems receive security updates promptly, particularly for widely used applications like Microsoft Office. Additional defensive measures include implementing email filtering solutions that can detect and block suspicious file attachments, configuring user training programs to recognize social engineering attempts, and establishing network monitoring to detect potential exploitation attempts. The mitigation strategy should also include reducing user privileges where possible, implementing application whitelisting policies, and maintaining regular system backups to ensure rapid recovery from potential compromise. These measures align with ATT&CK framework techniques related to privilege escalation and execution through office applications, emphasizing the importance of layered security approaches to protect against such vulnerabilities.