CVE-2026-64909
Summary
by MITRE • 08/11/2026
Integer underflow (wrap or wraparound) in Microsoft Office allows an unauthorized attacker to execute code locally.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/11/2026
Integer underflow vulnerabilities occur when an arithmetic operation results in a value that wraps around to a much smaller value than expected, typically due to unsigned integer overflow behavior. In the context of Microsoft Office applications, this specific vulnerability manifests when the software fails to properly validate integer values during processing operations, creating a condition where an attacker can manipulate input data to cause unexpected behavior. The flaw stems from insufficient boundary checking in memory allocation or buffer management routines where integer variables are used to determine array sizes, loop counters, or memory allocation amounts. When these integers underflow, they can result in unexpectedly small values being used for memory operations, potentially leading to buffer overflows or other memory corruption conditions that an attacker can exploit to execute arbitrary code with the privileges of the affected user.
The technical implementation of this vulnerability involves manipulating input parameters within Office document formats such as word processing files, spreadsheets, or presentation documents. Attackers craft malicious payloads that trigger integer underflow conditions during document parsing, typically by providing specially crafted numeric values that cause variables to wrap around to zero or negative values. This creates opportunities for memory corruption where the application attempts to allocate insufficient memory or access invalid memory regions. The vulnerability is particularly dangerous because it allows local code execution without requiring user interaction beyond opening the malicious document, making it a significant threat vector for targeted attacks. According to the common weakness enumeration framework, this maps directly to CWE-190, which specifically addresses integer overflow and underflow conditions.
The operational impact of this vulnerability extends beyond simple code execution as it provides attackers with persistent access to affected systems. Once successfully exploited, the attacker gains the ability to perform actions such as installing malware, modifying system files, accessing sensitive data, or establishing backdoors for continued access. The local execution requirement means that no network connectivity is needed for exploitation, making the vulnerability particularly dangerous in enterprise environments where users may open documents from untrusted sources. This type of vulnerability aligns with attack techniques described in the mitre att&ck framework under initial access and privilege escalation tactics, as it provides a method for attackers to gain a foothold on systems and potentially move laterally within networks.
Mitigation strategies for this vulnerability require immediate application of security patches from Microsoft, which typically involve implementing proper integer bounds checking and validation routines. Organizations should also deploy enhanced document filtering mechanisms that scan incoming Office documents for suspicious patterns or values that could trigger underflow conditions. Network segmentation and user access controls can limit potential damage if exploitation occurs, while endpoint detection and response solutions should monitor for anomalous memory allocation patterns or code execution behaviors that may indicate exploitation attempts. Regular security assessments and vulnerability scanning should focus on identifying systems running affected Office versions, and administrators should implement robust patch management processes to ensure timely deployment of security updates across all endpoints.