CVE-2025-54100: 
vulnerability analysis and mitigation

CVE-2025-54100 is a command injection vulnerability in Windows PowerShell that allows an unauthorized local attacker to execute arbitrary code. Classified under CWE-77 (Improper Neutralization of Special Elements used in a Command), it was disclosed and patched on December 9, 2025, as part of Microsoft's December Patch Tuesday security update cycle. The vulnerability affects a broad range of Windows versions, including Windows 10 (versions 1607, 1809, 21H2, 22H2), Windows 11 (versions 23H2, 24H2, 25H2), and Windows Server editions from 2008 through 2025. It carries a CVSS v3.1 base score of 7.8 (High) (Microsoft MSRC, Feedly).

The vulnerability stems from improper neutralization of special elements in commands processed by Windows PowerShell (CWE-77), enabling command injection. The attack vector is local, requires no privileges, but does require user interaction — suggesting the vulnerability may be triggered when a user executes a crafted script or interacts with a malicious PowerShell command. Post-patch behavior indicates the fix introduced an interactive prompt warning when running Invoke-WebRequest scripts, suggesting the injection vector may involve web-fetched or externally sourced script content (BleepingComputer, WindowsForum). Multiple public proof-of-concept exploits have been published on GitHub following the patch release (Feedly).

Successful exploitation results in high confidentiality, integrity, and availability impact on the affected system, enabling an attacker to execute arbitrary code in the context of the current user or system process. This can lead to complete system compromise, unauthorized data access and exfiltration, modification or destruction of system data, and potential lateral movement to other networked systems. The vulnerability's broad scope — affecting virtually all supported and some end-of-life Windows versions — significantly amplifies the potential attack surface (Microsoft MSRC, Feedly).

1. Reconnaissance: Identify target Windows systems running unpatched PowerShell versions (pre-December 9, 2025 updates) using asset inventory tools or network scanning.
2. Craft malicious payload: Prepare a PowerShell script or command containing specially crafted special characters or command delimiters that exploit the improper neutralization flaw (CWE-77), potentially embedded in a script fetched via Invoke-WebRequest or delivered through a phishing lure.
3. Deliver the payload: Trick the target user into executing the malicious PowerShell script — for example, via a phishing email with an attached .ps1 file, a malicious download link, or a compromised script repository.
4. Trigger command injection: When the victim executes the script, the injected command elements bypass PowerShell's input sanitization, causing the system to execute attacker-controlled commands locally.
5. Achieve code execution: The injected commands execute with the privileges of the running PowerShell process, potentially enabling privilege escalation, persistence mechanisms, data exfiltration, or lateral movement (Feedly, UndercodeTesting, GitHub PoC).

• Process: Unusual child processes spawned by powershell.exe or pwsh.exe, such as cmd.exe, net.exe, whoami.exe, curl.exe, or scripting interpreters; PowerShell processes executing with unexpected command-line arguments containing special characters or encoded payloads.
• Logs: Windows Event Log entries (Event ID 4104 – Script Block Logging) showing PowerShell scripts with suspicious command injection patterns or special delimiter characters; Event ID 4688 showing unexpected process creation chains originating from PowerShell.
• Network: Outbound connections from PowerShell processes to unknown or suspicious external IP addresses or domains, particularly following Invoke-WebRequest or Invoke-Expression calls; DNS queries for unusual domains initiated by PowerShell.
• File System: Unexpected .ps1 script files dropped in user temp directories (%TEMP%, %APPDATA%) or system directories; new scheduled tasks or registry run keys created by PowerShell processes.
• Registry: New entries under HKCU\Software\Microsoft\Windows\CurrentVersion\Run or HKLM\Software\Microsoft\Windows\CurrentVersion\Run created by PowerShell execution (Feedly, Qualys).

Microsoft released patches on December 9, 2025 as part of the December Patch Tuesday update. Specific patched build versions include: Windows 10 1607/Server 2016 (10.0.14393.8688+), Windows 10 1809/Server 2019 (10.0.17763.8146+), Windows 10 21H2 (10.0.19044.6691+), Windows 10 22H2 (10.0.19045.6691+), Windows 11 23H2 (10.0.22631.6345+), Windows Server 2022 (10.0.20348.4529+), Windows Server 2022 23H2 (10.0.25398.2025+), Windows 11 24H2/Server 2025 (10.0.26100.7456+), and Windows 11 25H2 (10.0.26200.7456+). Immediate prioritized actions include: applying the December 2025 cumulative updates to all affected systems, monitoring for suspicious PowerShell execution activity (especially commands with special characters), restricting PowerShell usage where not operationally necessary, implementing application whitelisting, and deploying EDR solutions to detect exploitation attempts (Microsoft MSRC, Feedly).

The vulnerability received significant coverage as part of Microsoft's December 2025 Patch Tuesday, which addressed 57 flaws including three zero-days. Security vendors including Tenable, Qualys, Rapid7, CrowdStrike, Sophos, and Malwarebytes published detailed analyses of the patch batch (Tenable, Qualys, Sophos). BleepingComputer noted that the patch introduced a new interactive warning in PowerShell when running Invoke-WebRequest scripts as a mitigation measure (BleepingComputer). Community discussion on Reddit and security forums highlighted the broad impact across Windows versions and the availability of public PoCs, with CVE-2025-54100 appearing in multiple "Top 10 Trending CVEs" lists in December 2025 and January 2026 (Reddit CVEWatch).