CVE-2026-50477 Overview
CVE-2026-50477 is a heap-based buffer overflow vulnerability in the Windows Kernel that allows an authorized local attacker to elevate privileges. The flaw is classified under [CWE-122] (Heap-based Buffer Overflow) and requires local access with low privileges to exploit. Successful exploitation results in a scope change, granting the attacker elevated privileges beyond the initially authorized security context. Microsoft published the advisory on July 14, 2026, and the vulnerability affects supported Windows Kernel components.
Critical Impact
An authenticated local attacker can trigger a heap-based buffer overflow in the Windows Kernel to gain elevated privileges, resulting in full compromise of confidentiality, integrity, and availability on the affected system.
Affected Products
- Microsoft Windows (Kernel component) — refer to the Microsoft CVE-2026-50477 Advisory for the complete list of affected builds
Discovery Timeline
- 2026-07-14 - CVE-2026-50477 published to NVD
- 2026-07-15 - Last updated in NVD database
Technical Details for CVE-2026-50477
Vulnerability Analysis
CVE-2026-50477 is a heap-based buffer overflow [CWE-122] in the Windows Kernel. Heap overflows in kernel space occur when the kernel writes data beyond the boundaries of a dynamically allocated pool buffer. The overflow corrupts adjacent kernel memory structures, including pool headers, object pointers, and function pointers.
An attacker who controls the overflow payload can overwrite kernel data structures to redirect execution flow or manipulate access control state. Because the flaw resides in the kernel, successful exploitation crosses the security boundary between low-privilege user mode and SYSTEM-level kernel execution. The scope change reflected in the CVSS vector indicates the impact extends beyond the vulnerable component.
Root Cause
The root cause is improper validation of input length or size arithmetic when allocating or writing to a heap-backed pool buffer inside the Windows Kernel. When the kernel processes an attacker-influenced request, it writes past the allocated boundary, corrupting adjacent pool memory. Microsoft has not published detailed component-level information beyond the advisory reference.
Attack Vector
Exploitation requires local access and low-privilege authentication on the target system. No user interaction is required. An attacker executes a crafted program that invokes the vulnerable kernel code path, typically through a system call, IOCTL, or kernel object interaction. The overflow is triggered during the kernel's handling of the crafted request, corrupting kernel pool memory and enabling privilege escalation to SYSTEM.
This vulnerability class is commonly weaponized after initial access, such as through phishing, malicious downloads, or supply chain compromise, to escape low-privilege contexts and establish persistence. Refer to the Microsoft CVE-2026-50477 Advisory for technical details.
Detection Methods for CVE-2026-50477
Indicators of Compromise
- Unexpected kernel pool corruption bugchecks such as BAD_POOL_HEADER (0x00000019) or KERNEL_MODE_HEAP_CORRUPTION (0x0000013A) on systems missing the July 2026 update
- Unsigned or unusual processes spawning child processes running as NT AUTHORITY\SYSTEM shortly after a low-privileged user logon
- New services, scheduled tasks, or driver installations created immediately following anomalous process token elevation events
Detection Strategies
- Monitor Windows Event Log ID 4672 (special privileges assigned) for accounts that should not normally receive SeDebugPrivilege or SeTcbPrivilege
- Correlate process creation events (Event ID 4688 / Sysmon Event ID 1) with parent-child token integrity mismatches
- Alert on unexpected kernel crashes and minidumps that indicate pool memory corruption on unpatched hosts
Monitoring Recommendations
- Enable Windows Defender Exploit Guard and Kernel-mode Hardware-enforced Stack Protection where supported
- Ingest Sysmon and Windows Security logs into a centralized SIEM for behavioral correlation of privilege escalation patterns
- Track patch compliance status across the fleet and prioritize systems that expose local logon access to multiple users
How to Mitigate CVE-2026-50477
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft CVE-2026-50477 Advisory to all affected Windows systems
- Prioritize patching multi-user systems, terminal servers, and shared workstations where local low-privilege access is broadly available
- Audit local account membership and remove unnecessary interactive logon rights to reduce the pool of potential attackers
Patch Information
Microsoft addressed CVE-2026-50477 in a security update published on July 14, 2026. Administrators should consult the Microsoft CVE-2026-50477 Advisory for the specific KB article, build numbers, and download links applicable to each Windows version deployed in the environment.
Workarounds
- No official workaround has been published by Microsoft. Apply the vendor-supplied security update as the primary remediation
- Restrict local logon rights and enforce the principle of least privilege to limit which users can attempt local exploitation
- Enable application allowlisting through Windows Defender Application Control or AppLocker to block execution of unsigned exploitation tooling
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
