CVE-2026-62416: Sharp Network Scanner Tool DoS Vulnerability

CVE-2026-62416 Overview

CVE-2026-62416 affects Sharp Corporation's Network Scanner Tool and Network Scanner Tool Lite. In the default configuration, both products accept incoming file uploads over the network without requiring authentication. Any attacker who can reach the listening service can push files to the host PC without restriction on volume or content.

This behavior maps to CWE-1188, Insecure Default Initialization of Resource. The exposure enables a denial-of-service (DoS) condition by exhausting local storage. It also enables staging of malicious files that a local user may later execute, extending the attack toward downstream systems.

Critical Impact
Unauthenticated remote attackers can flood a host running the Sharp scanner utilities with arbitrary files, causing storage exhaustion and providing a foothold for user-triggered malware execution.

Affected Products

Sharp Network Scanner Tool (initial configuration)
Sharp Network Scanner Tool Lite (initial configuration)
Windows PCs running the tools with default settings

Discovery Timeline

2026-08-03 - CVE-2026-62416 published to NVD
2026-08-03 - Last updated in NVD database

Technical Details for CVE-2026-62416

Vulnerability Analysis

The Network Scanner Tool and Network Scanner Tool Lite listen for incoming scan jobs from Sharp multifunction devices on the local network. In the shipped configuration, the receiving service performs no client authentication and applies no quota or size limit to incoming file transfers.

An attacker with network reachability to the host can send arbitrary files to the tool as if they were scanned documents. The attacker controls file name, file type, and volume. The tool writes each file to the configured local destination folder on the PC.

Two primary outcomes follow. First, an attacker can send files continuously until the target disk fills, producing a denial-of-service condition on the workstation. Second, the attacker can drop executable content, scripts, or lure documents into the folder. A local user browsing the destination folder may open or run the file, at which point code executes with that user's privileges and can pivot to other systems.

Root Cause

The root cause is an insecure default: the receiving service is enabled without authentication and without upload constraints. Security is deferred to the administrator, and the deployed default state exposes the host on any network the PC joins.

Attack Vector

Exploitation requires network access to the target PC and no user interaction for the DoS impact. The attacker connects to the tool's listening endpoint and issues successive upload requests. No credentials, tokens, or prior compromise are required. The follow-on execution scenario requires a local user to open the attacker-supplied file. Details are documented in the JVN Security Vulnerability Report and the Sharp Global Security Advisory.

Detection Methods for CVE-2026-62416

Indicators of Compromise

Unexpected growth of the Network Scanner Tool destination folder, especially outside business hours.
Files in the scan destination folder with executable extensions such as .exe, .js, .hta, .lnk, or macro-enabled Office documents.
Inbound network connections to PCs running the Sharp scanner utilities from hosts other than authorized Sharp multifunction printers.
Sudden low-disk-space alerts on workstations that host the scanner tool.

Detection Strategies

Alert on process writes to the Network Scanner Tool output directory by non-scanner processes or from network sockets bound to non-printer source addresses.
Correlate high-volume file creation events in the destination folder with the parent process of the scanner utility.
Flag execution of any binary or script that was written into the scan destination folder.

Monitoring Recommendations

Baseline the source IP addresses of legitimate Sharp multifunction devices and alert on scans arriving from any other source.
Monitor disk utilization on hosts running the tool and trigger on rapid consumption.
Log and review file-type distributions in the scan output folder on a recurring basis.

How to Mitigate CVE-2026-62416

Immediate Actions Required

Inventory all workstations running Network Scanner Tool or Network Scanner Tool Lite.
Reconfigure each installation to require authentication and to restrict accepted source devices, per Sharp guidance.
Restrict inbound access to the scanner tool's listening port to authorized Sharp MFP addresses using host or network firewall rules.
Review the scan destination folder on affected hosts for unexpected files and remove any that do not correspond to a known scan job.

Patch Information

Sharp Corporation has published guidance for CVE-2026-62416 in the Sharp Corporate Security Advisory and the Sharp Global Security Advisory. Administrators should apply the vendor-supplied updates or configuration changes described in those advisories on every host running either product.

Workarounds

Enable authentication in the Network Scanner Tool settings so that only known Sharp multifunction devices can push files.
Apply a host-based firewall rule that allows the tool's inbound port only from the IP addresses of trusted printers.
Place workstations that must run the tool on a segmented VLAN reachable only by authorized MFPs.
Disable or uninstall the tool on hosts that do not actively use network scanning.

bash

# Example Windows Defender Firewall rule: restrict scanner tool inbound to a trusted MFP
netsh advfirewall firewall add rule ^
  name="Sharp Network Scanner Tool - Trusted MFP Only" ^
  dir=in action=allow ^
  program="C:\Program Files\SHARP\Network Scanner Tool\NST.exe" ^
  remoteip=192.0.2.25 ^
  profile=domain,private

# Block all other inbound traffic to the scanner tool
netsh advfirewall firewall add rule ^
  name="Sharp Network Scanner Tool - Block Other" ^
  dir=in action=block ^
  program="C:\Program Files\SHARP\Network Scanner Tool\NST.exe"