Windows PowerShell Flaw Allows Attackers to Execute Malicious Code

A newly disclosed Windows PowerShell vulnerability allows attackers to execute malicious code on affected systems, putting organizations at heightened risk across Windows client and server environments. 

The vulnerability “… allows an unauthorized attacker to execute code locally,” said Microsoft in its advisory.

Industry experts also weighed in with their thoughts.

“This is especially concerning for scripts that rely on full HTML parsing, which may now prompt security warnings or fail entirely,” said Hüseyin Can Yüceel, Security Research lead at Picus Security.

Oliver Bilodeau, Principal Cybersecurity Researcher at Flare added, “We need to follow this vulnerability closely. Microsoft doesn’t have the habit of introducing changes that will break existing customer scripts, as this patch does. Right now, the public details are scarce, but we can imagine that specially crafted web pages can cause code to execute on the client side if called with Invoke-WebRequest.”

He also explained, “Public details and a low attack complexity score mean this vulnerability will attract threat actors’ attention.”

Understanding the PowerShell Risk

CVE-2025-54100 carries a CVSS score of 7.8 and potentially enables arbitrary code execution under the right conditions. 

In this case, PowerShell fails to correctly sanitize certain input sequences, allowing an attacker to embed malicious characters or payloads that alter the intended command structure. 

When processed, these specially crafted commands can break out of normal parsing rules and trigger unintended execution paths, effectively granting the attacker the ability to run arbitrary code within the context of the affected user.

While Microsoft currently rates the likelihood of exploitation as low, that assessment primarily reflects the need for local access and user interaction, such as enticing a victim to run a malicious script, open a tampered file, or execute a crafted command. 

However, public disclosure of the vulnerability changes the calculus: threat actors often use social engineering to bridge the local-access requirement, particularly in environments where PowerShell is used extensively for administrative or automated tasks.

Another factor elevating the risk is the vulnerability’s broad impact across nearly all supported Windows versions, including Windows 10, Windows 11, and Windows Server editions from 2008 through 2025. 

Because PowerShell underpins system administration, DevOps workflows, and security tooling, flaws in its command-processing logic can enable everything from lateral movement to privilege escalation in vulnerable environments.

The public disclosure of this flaw, combined with PowerShell’s broad use across enterprise environments, makes timely patching important. 

Even if exploitation requires specific conditions, attackers routinely combine smaller weaknesses to achieve broader impact, which heightens the need for proactive remediation.

How to Strengthen PowerShell Security

Organizations can reduce PowerShell-related risks by taking a layered approach that strengthens configuration, tightens access controls, and improves monitoring. 

• Apply the latest Microsoft security updates for all affected Windows versions and reboot systems as required.
• Enable advanced PowerShell protections, including script block logging, module logging, transcription logging, and other recommended security settings.
• Enforce least-privilege access for PowerShell, restrict administrative accounts, and disable outdated PowerShell versions when possible.
• Use application control solutions such as AppLocker or Windows Defender Application Control to ensure only trusted scripts can run.
• Monitor for unusual PowerShell activity, including encoded commands, unexpected script launches, and suspicious remoting behavior.
• Harden PowerShell execution policies and consider applying Constrained Language Mode or signature-based execution requirements.
• Train users and administrators to avoid running untrusted commands or files and support this with EDR or attack surface reduction rules that detect malicious PowerShell usage.

Together, these measures help organizations strengthen their PowerShell security posture by combining updates, configuration hardening, and monitoring to reduce misuse and improve detection of unusual activity. 

PowerShell’s Role in Organizational Risk

The disclosure of CVE-2025-54100 highlights the practical challenges organizations face in securing widely used administrative tools like PowerShell. 

Because PowerShell supports automation and system management across many environments, weaknesses in its core functionality can introduce risks that are important to address, even if exploitation is unlikely. 

As organizations continue to expand their automation and scripting workflows, maintaining timely updates and strong configuration practices helps ensure that isolated issues do not create broader operational impacts.

These challenges reinforce why organizations can benefit from adopting security models that assume no implicit trust, such as zero-trust principles.