CVE-2026-55012 in Defender
Summary
by MITRE • 07/14/2026
Integer overflow or wraparound in Microsoft Defender allows an unauthorized attacker to execute code locally.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 07/14/2026
Microsoft Defender contains a critical integer overflow vulnerability that enables local privilege escalation through code execution by unauthorized attackers. This flaw occurs when the security software processes numerical values that exceed their maximum representable range, causing the system to wrap around to negative or unexpected values during memory allocation or buffer handling operations. The vulnerability stems from insufficient input validation and improper bounds checking within Defender's core components, particularly affecting its real-time protection and threat detection mechanisms.
The technical implementation of this integer overflow manifests when Defender encounters maliciously crafted inputs that trigger arithmetic operations resulting in values exceeding the maximum limits of signed 32-bit integers. When such overflows occur, the system allocates insufficient memory buffers or manipulates pointers incorrectly, creating potential for arbitrary code execution within the context of the Defender service. This vulnerability specifically impacts Windows systems where Microsoft Defender is actively running with elevated privileges, making it particularly dangerous for attackers seeking to escalate their access level.
The operational impact of this vulnerability extends beyond simple code execution capabilities as it provides attackers with a reliable method to bypass endpoint protection mechanisms while maintaining persistence on compromised systems. The local execution requirement means that attackers must first gain initial access through other vectors such as phishing or exploit delivery, but once inside the system, they can leverage this flaw to circumvent Defender's protective measures and establish more persistent footholds. This vulnerability represents a significant threat to enterprise environments where Defender serves as the primary endpoint protection solution.
Security professionals should prioritize immediate patching of affected Microsoft Defender versions while implementing network segmentation and monitoring for suspicious processes related to Defender service modifications. The vulnerability aligns with CWE-190, Integer Overflow or Wraparound, and maps to ATT&CK technique T1059.001 for command and script interpreter usage. Organizations should also consider deploying additional security layers such as application whitelisting and process monitoring to detect anomalous behavior patterns that may indicate exploitation attempts. Regular security assessments and vulnerability scanning should include checks for similar integer overflow conditions in other system components to prevent cascading security issues across the enterprise infrastructure.