Microsoft PowerShell Critical Flaw CVE-2026-83578 Allows Remote Code Execution via Integer Underflow

A new 9.8-rated vulnerability in Windows PowerShell enables unauthorized network attackers to run code, according to Microsoft and the NVD.

Threat Times Exposure DeskOctober 14, 20262 min read

Share LinkedIn Reddit

Illustration: A sleek black Windows tower sits isolated on a dark desk. — AI-generated illustration: Threat Times

Key points

CVE-2026-83578 is rated 9.8 Critical by the National Vulnerability Database.
The flaw stems from an integer underflow in Windows PowerShell.
Attackers can execute code over a network without authorization.

Microsoft has identified a critical remote code execution vulnerability in Windows PowerShell, designated CVE-2026-83578. According to the Microsoft Security Update Guide, this flaw allows an unauthorized attacker to execute code over a network by exploiting an integer underflow issue within the software.

The National Vulnerability Database assigns a CVSS score of 9.8 to this vulnerability, classifying it as Critical. The advisory links the issue to weaknesses CWE-122, CWE-190, and CWE-191. Microsoft states that the integer underflow, also described as a wrap or wraparound error, is the mechanism enabling the unauthorized remote execution of code.

Technical Context

The vulnerability specifically impacts Windows PowerShell, a task automation and configuration management framework. The Microsoft advisory notes that the integer underflow occurs within the component itself. The National Vulnerability Database record confirms that this specific flaw allows for remote code execution over a network, highlighting the severity of the exploit path.

The associated Common Weakness Enumerations include CWE-191 (Integer Underflow/Wraparound), CWE-190 (Integer Overflow or Wraparound), and CWE-122 (Heap-based Buffer Overflow). These classifications suggest that the underlying issue involves improper handling of integer values, leading to memory corruption or logic errors that an attacker can leverage to run arbitrary commands on the affected system.

Who Is Affected

Windows PowerShell users are the primary targets of this vulnerability. The Microsoft Security Update Guide lists Windows PowerShell as the affected component for CVE-2026-83578. Any system running the vulnerable version of this software is potentially exposed to the described remote code execution risk if network access is available to the attacker.

The source material does not specify which versions of Windows PowerShell are affected, nor does it list specific operating system versions. However, the presence of the vulnerability in the PowerShell component indicates that any environment relying on this tool for scripting or management could be at risk. Organizations using PowerShell for administrative tasks should review their exposure to network-based attacks.

What should you do?

Security professionals should monitor for official patches from Microsoft regarding CVE-2026-83578. Until a fix is confirmed and deployed, organizations should assess their network segmentation to limit access to systems running Windows PowerShell. Monitoring network traffic for unusual PowerShell execution patterns can help detect potential exploitation attempts.

What to do and how to stay safe: Microsoft

Check Microsoft Security Update Guide for patch availability for CVE-2026-83578.
Restrict network access to systems running Windows PowerShell to authorized users only.
Monitor logs for unauthorized PowerShell execution attempts over the network.
Ensure systems are up to date with previous security updates to reduce overall risk.

Step-by-step guide: Risk-Based Vulnerability Management: Prioritize Fixes by Actual Danger

General security guidance from the Threat Times newsroom. It is not confirmed advice from the organisations named in this story.