CVE-2026-77904 in Windows
Summary
by MITRE • 09/09/2026
Heap-based buffer overflow in Windows Volume Manager Extension Driver allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified involves a heap-based buffer overflow within the Windows Volume Manager Extension Driver, commonly referred to as volmgrext.sys. This specific component of the Microsoft Windows operating system is responsible for managing virtual disk operations and handling interactions between user-mode applications and kernel-mode drivers that manipulate volume structures. The flaw arises from an improper validation of input data lengths during the processing of certain IOCTL (Input/Output Control) requests sent by authorized local users to this driver. When a crafted request containing oversized or malformed data is processed, the driver fails to correctly bound-check the buffer size before copying the data into heap memory allocated for handling volume management tasks. This lack of rigorous boundary checking allows an attacker to write beyond the intended limits of the allocated heap buffer, overwriting adjacent memory structures that are critical for system stability and security enforcement mechanisms such as control flow integrity or exception handler chains.
From a technical perspective, this vulnerability is classified under CWE-122: Heap-based Buffer Overflow, which represents one of the most dangerous classes of software defects due to its potential for arbitrary code execution. The exploitation mechanism typically involves carefully crafting the overflow payload to overwrite function pointers or object headers within the heap metadata. By manipulating these overwritten structures, an attacker can achieve control over the instruction pointer during subsequent memory operations triggered by the operating system. This capability enables a local privilege escalation attack where a low-privileged user process transitions into executing code with SYSTEM-level privileges. The impact is severe because it bypasses standard access controls and allows full compromise of the host machine without requiring physical access or remote network interaction, provided the attacker has valid credentials on the target system.
In terms of threat intelligence mapping, this vulnerability aligns with MITRE ATT&CK technique T1068: Exploitation for Privilege Escalation, specifically within the context of local exploitation scenarios where attackers leverage software vulnerabilities to gain higher-level access. It also relates to CWE-270: Privilege Context Mismanagement if the driver fails to properly validate the security context of the caller before processing sensitive volume operations. The operational impact extends beyond simple privilege escalation; successful exploitation can lead to complete system compromise, including data exfiltration, installation of persistent backdoors, and lateral movement within a network environment where this compromised host serves as a pivot point. Security analysts must recognize that heap-based overflows in kernel drivers are particularly critical because they operate at Ring 0, the highest privilege level on x86 architectures, making detection by standard endpoint security solutions difficult once memory corruption occurs.
Mitigation strategies for this vulnerability primarily involve applying the latest cumulative updates and security patches released by Microsoft to ensure the volmgrext.sys driver is updated with proper input validation logic. Organizations should enforce strict patch management policies to minimize the window of exposure. Additionally, implementing application control technologies such as Windows Defender Application Control or third-party solutions can restrict the execution of unsigned drivers and limit the ability of untrusted applications to interact with kernel-mode components via IOCTL requests. Enabling Kernel DMA Protection and Memory Integrity features in systems that support hardware-assisted virtualization provides an additional layer of defense by preventing unauthorized modifications to executable code in memory, thereby mitigating the impact even if a buffer overflow is successfully exploited. Regular auditing of driver signatures and monitoring for anomalous kernel-mode activity can also aid in early detection of exploitation attempts targeting this class of vulnerabilities.