CVE-2026-70329
Summary
by MITRE • 08/11/2026
Integer overflow or wraparound in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability represents a critical integer overflow condition that can be exploited to achieve remote code execution within Microsoft Office Outlook applications. The flaw occurs when the application processes certain malformed data structures that trigger arithmetic operations resulting in integer wraparound behavior. Such conditions typically arise when unsigned integers exceed their maximum allowable values and wrap back to zero or negative numbers, creating unpredictable program states that attackers can manipulate for malicious purposes.
The technical implementation of this vulnerability involves scenarios where Outlook handles email messages or attachments containing crafted numeric values that cause buffer calculations to overflow. When the application attempts to allocate memory or process data structures based on these manipulated integer values, it can lead to memory corruption that allows attackers to control execution flow. This type of vulnerability falls under the common weakness enumeration CWE-190 which specifically addresses integer overflow and wraparound conditions, particularly in contexts where arithmetic operations are performed without proper bounds checking.
From an operational perspective, this vulnerability enables remote code execution attacks that can be delivered through malicious email messages or network-based payloads. Attackers can craft specially designed emails with malformed attachment headers, embedded objects, or script content that triggers the integer overflow during parsing operations. The attack vector typically requires no user interaction beyond opening the malicious message, making it particularly dangerous for enterprise environments where email remains a primary communication channel. According to ATT&CK framework technique T1203, this vulnerability represents a remote access capability that can be leveraged for persistent compromise of affected systems.
The impact extends beyond simple code execution as successful exploitation can lead to complete system compromise and lateral movement within network environments. Organizations using Outlook in conjunction with Exchange Server or other Microsoft collaboration platforms face heightened risk due to the widespread deployment of these applications across enterprise networks. The vulnerability's network-based nature means that attackers can initiate attacks from external positions without requiring physical access to target systems, making it particularly attractive for advanced persistent threat campaigns.
Mitigation strategies should include immediate deployment of Microsoft security patches and updates as well as network segmentation to limit exposure of vulnerable Outlook installations. Organizations should implement email filtering solutions that can detect and quarantine potentially malicious content before it reaches end users. Additionally, security monitoring should focus on unusual memory allocation patterns or process behavior that might indicate exploitation attempts. The vulnerability highlights the importance of robust input validation and proper integer handling in enterprise applications, particularly those processing untrusted data from network sources. Regular security assessments and code reviews focusing on arithmetic operations and buffer management can help identify similar conditions that may exist in other application components.