CVE-2026-50347: Windows 10 1607 Buffer Overflow Flaw

CVE-2026-50347 Overview

CVE-2026-50347 is a heap-based buffer overflow [CWE-122] in a Microsoft Windows Data dynamic-link library (DLL). An unauthorized attacker can exploit the flaw to execute arbitrary code locally on affected systems. Exploitation requires user interaction, such as opening a crafted file that is processed by the vulnerable component. Microsoft has published a security update through the Microsoft Security Response Center (MSRC) advisory portal.

The vulnerability affects a broad set of supported Windows client and server releases, including Windows 10, Windows 11, and Windows Server editions from 2012 through 2025. Successful exploitation grants the attacker the ability to run code in the context of the targeted user, with high impact to confidentiality, integrity, and availability.

Critical Impact
Local code execution on all currently supported Windows client and server versions, with full compromise of confidentiality, integrity, and availability of the affected host.

Affected Products

Microsoft Windows 10 (1607, 1809, 21H2, 22H2) across x86, x64, and ARM64 architectures
Microsoft Windows 11 (24H2, 25H2, 26H1) across x64 and ARM64 architectures
Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025

Discovery Timeline

2026-07-14 - CVE-2026-50347 published to the National Vulnerability Database (NVD)
2026-07-20 - Last updated in NVD database

Technical Details for CVE-2026-50347

Vulnerability Analysis

The flaw is a heap-based buffer overflow [CWE-122] inside a Windows Data DLL responsible for parsing structured data. When the affected library processes a specially crafted input, it writes beyond the bounds of an allocated heap buffer. This out-of-bounds write corrupts adjacent heap metadata or object pointers, enabling an attacker to influence control flow.

Because the attack vector is local and requires user interaction, exploitation typically involves convincing a user to open a malicious file or invoke an application that loads the vulnerable DLL. Once triggered, the attacker gains code execution in the context of the logged-in user. Combined with a separate privilege escalation, this primitive can lead to full system compromise.

The Exploit Prediction Scoring System (EPSS) reports a probability of 0.444% as of 2026-07-20, and no public proof-of-concept has been observed at the time of publication.

Root Cause

The root cause is missing or insufficient bounds validation when the Windows Data DLL copies attacker-controlled data into a fixed-size heap allocation. The parser trusts a length or offset field derived from untrusted input, resulting in a heap write past the allocated region. Microsoft's advisory identifies the weakness class as [CWE-122] Heap-based Buffer Overflow.

Attack Vector

An attacker must deliver a malicious data file or content stream that is processed by an application invoking the vulnerable DLL. Common delivery methods include email attachments, malicious downloads, or removable media. The victim must open or preview the file for the vulnerable parser to execute. No prior authentication to the target is required, but local execution context is necessary.

No verified public exploit code is available. Refer to the Microsoft Security Update Guide for CVE-2026-50347 for authoritative technical details.

Detection Methods for CVE-2026-50347

Indicators of Compromise

Unexpected crashes, Windows Error Reporting (WER) entries, or Application event log faults referencing the Windows Data DLL parser module.
Child processes spawned by document-handling or shell applications that then execute cmd.exe, powershell.exe, or unsigned binaries from user-writable directories.
Newly created files or scheduled tasks in %AppData%, %Temp%, or %ProgramData% immediately after a user opens an untrusted data file.

Detection Strategies

Hunt for anomalous heap corruption crashes tied to the vulnerable DLL by correlating WER telemetry with process ancestry.
Monitor for suspicious process trees where user-facing applications load the Windows Data DLL and subsequently execute scripting engines or LOLBins.
Apply behavioral rules that identify post-exploitation actions such as credential access, persistence creation, or lateral movement following a document open event.

Monitoring Recommendations

Ingest Sysmon Event IDs 1 (process create), 7 (image load), and 11 (file create) into the SIEM and alert on the vulnerable DLL loading into unusual host processes.
Track Windows security patch deployment status across all endpoints and servers to identify unpatched systems exposed to CVE-2026-50347.
Enable Attack Surface Reduction (ASR) rules and audit their events to detect exploitation attempts against Office and script hosts.

How to Mitigate CVE-2026-50347

Immediate Actions Required

Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-50347 to all affected Windows client and server systems.
Prioritize patching of multi-user systems, jump hosts, and endpoints belonging to privileged users where local code execution has the highest downstream impact.
Restrict execution of untrusted files delivered by email, web download, or removable media until patches are deployed.

Patch Information

Microsoft has released fixes through the standard monthly security update channel. Administrators should deploy the update via Windows Update, Windows Server Update Services (WSUS), Microsoft Update Catalog, or Microsoft Intune. Confirm patch installation by validating the corresponding Knowledge Base article listed in the MSRC advisory and by verifying the file version of the affected Windows Data DLL on remediated hosts.

Workarounds

Enforce least privilege so that users do not run with local administrator rights, limiting the blast radius of successful exploitation.
Enable Microsoft Defender Attack Surface Reduction rules that block Office and script hosts from spawning child processes.
Use application control policies such as Windows Defender Application Control (WDAC) or AppLocker to prevent execution of unsigned binaries from user-writable locations.

bash

# Verify patch status on Windows hosts using PowerShell
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10

# Query Windows Update history for the CVE-2026-50347 KB
wmic qfe list brief /format:table