CVE-2026-78453: Windows SCSI Information Disclosure Flaw

CVE-2026-78453 Overview

CVE-2026-78453 is an integer underflow vulnerability in the Microsoft Windows SCSI Class System File. The flaw allows an unauthenticated remote attacker to disclose sensitive information over a network when a user performs an action. The weakness is classified as [CWE-191] Integer Underflow (Wrap or Wraparound). Successful exploitation results in high confidentiality impact without affecting integrity or availability.

Critical Impact
Remote attackers can trigger an integer underflow in the Windows SCSI Class System File to disclose memory contents over a network, provided a user interacts with attacker-supplied content.

Affected Products

Microsoft Windows (SCSI Class System File component)
Specific build and version details are published in the Microsoft Security Update Guide
Refer to the Microsoft Security Update Guide for CVE-2026-78453 for the authoritative product list

Discovery Timeline

2026-09-08 - CVE-2026-78453 published to the National Vulnerability Database
2026-09-08 - Last updated in the NVD database

Technical Details for CVE-2026-78453

Vulnerability Analysis

The vulnerability resides in the Windows SCSI Class System File, a kernel-mode component responsible for handling Small Computer System Interface (SCSI) class device operations. An arithmetic operation on an untrusted input underflows below its minimum representable value and wraps to a large unsigned quantity. The resulting incorrect size or offset causes the component to read beyond an intended buffer boundary. Read data can then be returned to the network-reachable attacker, leaking kernel or process memory.

Exploitation requires user interaction, which typically means the victim must open, browse, or connect to attacker-controlled content that reaches the vulnerable code path. Because the attack vector is Network with low complexity and no privileges required, an attacker can stage the interaction remotely without prior access. The scope remains unchanged, and only confidentiality is affected.

Root Cause

The root cause is unchecked arithmetic on a length or index field within SCSI class processing. When an attacker-controlled value is subtracted below zero, the unsigned result wraps to a very large number. Subsequent memory operations use that wrapped value, violating buffer boundaries and exposing adjacent memory.

Attack Vector

An attacker crafts malformed SCSI-related data reachable over a network path that the Windows SCSI Class System File parses. The victim must perform an action such as connecting to a malicious resource or opening a crafted file. When the underflow triggers, the system returns memory contents that the attacker observes across the network. No verified proof-of-concept exploit is publicly available at the time of publication.

See the Microsoft Security Update Guide for CVE-2026-78453 for authoritative technical detail.

Detection Methods for CVE-2026-78453

Indicators of Compromise

Unexpected SCSI class driver errors or crash dumps referencing the SCSI Class System File
Anomalous inbound or outbound network sessions targeting Windows storage-related services
Repeated malformed SCSI protocol data units delivered to Windows hosts
Unusual file open or mount actions initiated by users against untrusted network resources

Detection Strategies

Monitor Windows Event Log entries for storage subsystem faults, driver errors, and abnormal termination of processes touching SCSI class devices
Inspect network telemetry for unusual traffic patterns to hosts serving SCSI or storage-adjacent content
Correlate user interaction events (file opens, URL clicks, drive mounts) with subsequent storage driver anomalies
Deploy endpoint detection tooling that flags kernel-mode read violations and out-of-bounds memory access attempts

Monitoring Recommendations

Enable verbose logging on storage stack components and forward events to a centralized SIEM
Baseline normal SCSI driver behavior and alert on statistically significant deviations
Track patch state for the Windows SCSI Class System File across all managed endpoints and servers
Alert on repeated user interactions with untrusted external resources that precede storage driver anomalies

How to Mitigate CVE-2026-78453

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft Security Update Guide for CVE-2026-78453 as soon as testing permits
Inventory Windows systems that expose or consume SCSI class functionality and prioritize patch deployment
Restrict user interaction with untrusted network resources through email, web, and content filtering controls
Increase monitoring on internet-facing Windows hosts until patches are applied

Patch Information

Microsoft addresses this vulnerability through the security update published in the Microsoft Security Update Guide. Administrators should consult the Microsoft Security Update Guide for CVE-2026-78453 to identify the correct package for each affected Windows build and deploy through Windows Update, WSUS, Microsoft Endpoint Configuration Manager, or Intune.

Workarounds

Limit outbound network access to trusted destinations to reduce the likelihood of user interaction with attacker-controlled resources
Enforce least-privilege browsing and email handling to reduce exposure of high-value hosts
Segment storage and management networks so SCSI-related traffic remains within trusted zones
Deploy attack surface reduction rules that block untrusted content from launching or being processed by system components

bash

# Configuration example: verify patch state on Windows endpoints
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20

# Example: query for recent storage driver faults in the System event log
Get-WinEvent -LogName System -MaxEvents 500 |
  Where-Object { $_.ProviderName -match 'scsi|storahci|storport' } |
  Format-Table TimeCreated, Id, LevelDisplayName, Message -AutoSize