CVE-2026-55121 in Office
Summary
by MITRE • 07/14/2026
Out-of-bounds read in Microsoft Office allows an unauthorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 07/15/2026
This vulnerability represents a critical out-of-bounds read flaw within Microsoft Office applications that enables unauthorized attackers to extract sensitive information from the local system. The technical nature of this issue stems from insufficient bounds checking in memory operations where the application fails to validate array indices or buffer limits before accessing memory locations. Such deficiencies create opportunities for attackers to manipulate input data or exploit existing code paths to read memory beyond allocated boundaries, potentially exposing confidential information stored in adjacent memory regions.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can serve as a foundational weakness for more sophisticated attacks. Attackers leveraging this flaw can potentially extract encryption keys, credentials, temporary files, or other sensitive data that resides in memory. This type of vulnerability falls under the CWE-129 category of Improper Input Validation, specifically manifesting as an out-of-bounds read condition that violates fundamental memory safety principles. The attack surface is particularly concerning given Microsoft Office's widespread deployment across enterprise environments where users frequently interact with potentially malicious documents.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter and T1566.001 for Phishing, as attackers typically deliver malicious Office documents through social engineering campaigns. The local information disclosure capability means that even if initial compromise requires user interaction, the vulnerability can be exploited to gather additional intelligence about the target system. This makes it particularly dangerous in environments where Office applications are frequently used with elevated privileges or when users have access to sensitive corporate data.
Mitigation strategies should focus on immediate patch deployment as the primary defense mechanism, alongside broader security controls including email filtering solutions, application whitelisting policies, and user education programs. Organizations should implement strict document handling procedures that limit the execution of untrusted Office files in production environments. The vulnerability also underscores the importance of regular security assessments and penetration testing to identify similar memory safety issues across the organization's software portfolio. Additionally, implementing runtime protections such as address space layout randomization and data execution prevention can significantly reduce the exploitability of such memory corruption vulnerabilities.