CVE-2026-20846 in Windows
Summary
by MITRE • 02/10/2026
Buffer over-read in Windows GDI+ allows an unauthorized attacker to deny service over a network.
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Analysis
by VulDB Data Team • 02/11/2026
The vulnerability identified as CVE-2026-20846 represents a critical buffer over-read condition within the Windows Graphics Device Interface Plus component that enables remote attackers to execute denial of service attacks. This flaw exists in the GDI+ graphics processing subsystem that handles various image formats and graphical operations across the Windows operating system. The buffer over-read occurs when the system processes malformed or specially crafted graphic data structures that exceed expected memory boundaries during image rendering operations. The vulnerability specifically manifests when GDI+ attempts to read memory locations beyond the allocated buffer space, potentially causing system instability or complete service disruption.
This security flaw operates at the kernel level within the Windows graphics subsystem and presents significant operational risks for enterprise environments where network-based graphic processing is common. The over-read condition can be triggered through various attack vectors including malicious image files, web content rendering, or document processing that utilizes GDI+ for graphical operations. When exploited, the vulnerability allows unauthorized remote actors to cause system crashes, application failures, or complete system hangs that effectively deny service to legitimate users. The attack requires minimal privileges and can be executed through network-based delivery mechanisms, making it particularly dangerous in corporate environments where users frequently access external content.
The technical implementation of this vulnerability stems from inadequate input validation within the GDI+ image processing routines that fail to properly bounds-check data structures before memory access operations. This type of flaw falls under CWE-129, which specifically addresses insufficient input validation allowing for buffer overflows and over-reads. The vulnerability's exploitation pattern aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through system resource exhaustion or corruption. The flaw demonstrates a classic buffer management issue where the system does not adequately verify the size or integrity of graphic data before processing, leading to memory corruption that can be leveraged for service disruption.
Organizations affected by this vulnerability should implement immediate mitigations including applying the relevant Microsoft security patches as soon as they become available, implementing network segmentation to limit access to systems that process external graphic content, and deploying intrusion detection systems to monitor for suspicious graphic file processing activities. Additionally, administrators should consider disabling unnecessary graphic processing capabilities where possible and implementing strict content filtering for external image files. The vulnerability's impact extends beyond simple denial of service as it could potentially provide a foothold for more sophisticated attacks if combined with other exploitation techniques. Regular security assessments should focus on identifying systems that utilize GDI+ for processing untrusted graphic content, particularly web servers, email gateways, and document processing systems that may be vulnerable to this specific buffer over-read condition.