CVE-2026-54124

What it actually does

CVE-2026-54124 is a local code execution vulnerability caused by an integer overflow or wraparound condition in Windows Terminal. A crafted input or terminal-handling condition can cause incorrect memory sizing or bounds calculations, potentially leading to memory corruption and execution of attacker-controlled code in the context of the user running Windows Terminal. The CVSS vector indicates local attack access, low attack complexity, no privileges required, and required user interaction, with high confidentiality, integrity, and availability impact.

Why it matters to the business

Successful exploitation can allow an attacker who can convince a user to open or interact with malicious terminal content to run code on the affected workstation or server as that user. This could lead to malware execution, credential theft, lateral movement tooling, tampering with files, or persistence under the user context. Because Windows Terminal is common across Windows client and server platforms, exposure may be broad where affected Windows versions or Microsoft Terminal installations are present. The vulnerability is not currently listed in CISA KEV and has no known public exploit maturity in the provided data, but the high impact and low complexity make timely patching important.

How an attack unfolds

An attacker first needs a way to reach a target user locally or induce the user to interact with malicious terminal-related content, such as opening a crafted terminal profile, command sequence, file, shortcut, repository, script, or output stream designed to trigger the vulnerable code path in Windows Terminal. When Windows Terminal processes the crafted data, an integer calculation overflows or wraps, causing memory to be allocated, indexed, or copied incorrectly. The resulting memory corruption can be shaped to redirect execution flow and run attacker-controlled code in the context of the interactive user. After code execution, the attacker may launch additional processes, drop payloads, harvest credentials or tokens available to the user, establish persistence, and move laterally if the compromised user has access to other systems.

How to fix it

Apply the Microsoft security update that addresses CVE-2026-54124 for all affected Windows and Microsoft Terminal installations as soon as it is available through Windows Update, Microsoft Update Catalog, WSUS, Intune, or enterprise patch management tooling. Because no exact fixed versions were provided, verify remediation against Microsoft’s official security update guide for the affected product and operating system build. Prioritize patching interactive workstations, developer systems, administrative jump hosts, and servers where users run Windows Terminal. Until patched, reduce exposure by limiting use of Windows Terminal for untrusted files or repositories, blocking execution of unsolicited scripts and shortcuts, disabling or restricting untrusted terminal profiles, and enforcing least privilege so exploitation runs with minimal user rights. Application control, attack surface reduction rules, endpoint protection, and monitoring for suspicious child processes spawned from Windows Terminal can reduce post-exploitation impact but should not be treated as a substitute for patching.

How to confirm the fix worked

Confirm that affected Windows systems have installed the relevant Microsoft security update for CVE-2026-54124 and that the OS build or Microsoft Terminal package version is at or above the fixed level documented by Microsoft. Use enterprise inventory to identify systems with Microsoft Terminal or Windows Terminal installed, including Windows 10 21H2/22H2, Windows 11 24H2/25H2/26H1, Windows Server 2022, and Windows Server 2025. Validate patch deployment through Windows Update history, installed hotfix inventory, Microsoft Store or winget package inventory where applicable, and vulnerability scanner checks. After remediation, attempt to reproduce only in a controlled test environment using vendor-approved validation or scanner logic; do not run untrusted exploit code in production. Confirm that endpoint telemetry no longer shows vulnerable package/build detections and that no policy exceptions are leaving high-risk systems unpatched.

Typical attack path

1. Identify targets using affected versions of Windows Terminal or affected Windows releases.
2. Prepare crafted terminal-related content that triggers the integer overflow or wraparound condition.
3. Deliver the content through a local interaction path, such as a malicious project, script, shortcut, archive, terminal profile, or command output that the user opens in Windows Terminal.
4. The user opens or interacts with the crafted content, satisfying the user-interaction requirement.
5. Windows Terminal processes the crafted data and hits the vulnerable integer calculation.
6. Memory corruption occurs and attacker-controlled code executes as the current user.
7. The attacker launches follow-on tooling, drops payloads, steals accessible credentials or data, or establishes persistence.
8. If valuable privileges or network access are available, the attacker attempts lateral movement or privilege escalation using separate techniques.

How to detect it

To determine whether exploitation may already have occurred, review endpoint detection telemetry, Windows Event Logs, crash reports, and process creation logs for suspicious activity involving Windows Terminal. Focus on WindowsTerminal.exe, wt.exe, and OpenConsole.exe spawning unusual child processes such as powershell.exe, pwsh.exe, cmd.exe, wscript.exe, cscript.exe, mshta.exe, rundll32.exe, regsvr32.exe, certutil.exe, bitsadmin.exe, curl.exe, wget.exe, or unknown executables from user-writable directories. Review Windows Error Reporting and Application event logs for crashes of WindowsTerminal.exe or OpenConsole.exe, especially crashes followed immediately by new process creation, file writes, network connections, privilege escalation attempts, or persistence changes. Examine terminal profile changes, recently opened files, downloaded archives, repositories, scripts, .lnk files, and user-writable payload locations around the time of suspicious crashes. Useful log sources include Sysmon process creation and network events, Windows Security Event ID 4688 if command-line auditing is enabled, Microsoft Defender for Endpoint advanced hunting data, EDR process trees, Windows Application logs, Windows Error Reporting artifacts, PowerShell logs, and file creation telemetry. There are no known public exploit-specific indicators in the provided data, so detection should be behavior-based rather than signature-only.

• WindowsTerminal.exe spawning powershell.exe
• WindowsTerminal.exe spawning pwsh.exe
• WindowsTerminal.exe spawning cmd.exe
• WindowsTerminal.exe spawning wscript.exe
• WindowsTerminal.exe spawning cscript.exe
• WindowsTerminal.exe spawning mshta.exe
• WindowsTerminal.exe spawning rundll32.exe
• WindowsTerminal.exe spawning regsvr32.exe
• WindowsTerminal.exe spawning certutil.exe
• WindowsTerminal.exe spawning bitsadmin.exe
• WindowsTerminal.exe spawning curl.exe
• WindowsTerminal.exe spawning wget.exe
• wt.exe spawning powershell.exe
• wt.exe spawning pwsh.exe
• wt.exe spawning cmd.exe
• OpenConsole.exe spawning powershell.exe
• OpenConsole.exe spawning pwsh.exe
• OpenConsole.exe spawning cmd.exe
• Faulting application name: WindowsTerminal.exe
• Faulting application name: OpenConsole.exe
• %LOCALAPPDATA%\Packages\Microsoft.WindowsTerminal_8wekyb3d8bbwe\LocalState\settings.json
• %LOCALAPPDATA%\Packages\Microsoft.WindowsTerminalPreview_8wekyb3d8bbwe\LocalState\settings.json

What your security team should do

• Inventory all endpoints and servers running affected Windows releases or Microsoft Terminal and identify systems where Windows Terminal is installed or commonly used.
• Patch affected systems using the Microsoft security update for this vulnerability, prioritizing developer workstations, administrator workstations, jump boxes, and systems used to access sensitive environments.
• Monitor for suspicious process trees where WindowsTerminal.exe, wt.exe, or OpenConsole.exe launches scripting engines, shells, downloaders, credential tools, or unexpected binaries.
• Hunt for recent Windows Terminal crashes followed by process creation, file drops, network connections, or authentication activity from the same user session.
• Use application control or endpoint protection policy to restrict unsigned or untrusted payload execution from user-writable directories.
• Educate users, especially developers and administrators, not to open untrusted terminal profiles, scripts, shortcuts, archives, or repositories until patching is complete.
• Track Microsoft advisories for exact fixed versions and any change in exploit maturity, KEV status, or ransomware use.
• If suspicious exploitation is suspected, isolate the endpoint, preserve crash dumps and endpoint telemetry, collect relevant Windows event logs, and rotate credentials exposed in the compromised user context.