CVE-2026-55948 in Office
Summary
by MITRE • 07/14/2026
Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
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Analysis
by VulDB Data Team • 07/14/2026
This vulnerability represents a critical use-after-free flaw in Microsoft Office Excel that enables arbitrary code execution within the context of the current user's privileges. The vulnerability arises when Excel improperly handles memory management during object disposal, creating a scenario where freed memory blocks can be accessed and manipulated by malicious actors. Such flaws typically occur when the application fails to properly invalidate pointers or references after memory has been released, allowing an attacker to overwrite freed memory with malicious code that will execute when the object is subsequently accessed. The technical nature of this vulnerability aligns with common software security weaknesses classified under CWE-416 which specifically addresses use-after-free conditions in memory management operations.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with a pathway to achieve persistent local code execution without requiring elevated system privileges. An attacker could craft malicious Excel files that trigger the vulnerable code path during normal document processing, potentially leading to full system compromise through exploitation of the use-after-free condition. This type of vulnerability particularly affects enterprise environments where Microsoft Office applications are widely deployed and frequently used for business operations. The attack vector typically involves social engineering campaigns where users unknowingly open malicious Excel documents, making this a significant concern for organizations with limited endpoint protection capabilities.
Security practitioners should implement multiple layers of defense to mitigate the risk associated with this vulnerability. Immediate remediation through Microsoft security updates represents the primary mitigation strategy, as these patches address the underlying memory management flaws in Excel's object handling routines. Organizations should also deploy application whitelisting solutions and restrict user permissions to prevent unauthorized execution of potentially malicious code. Network-based protections including firewall rules and intrusion detection systems can help identify and block attempts to deliver exploit payloads through email attachments or web downloads. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1059 which covers command and scripting interpreter usage, as successful exploitation would likely involve executing malicious code within the target system. Additionally, monitoring for unusual memory access patterns and object allocation behaviors can help detect exploitation attempts in real-time environments where traditional signature-based detection may not be sufficient.