CVE-2026-24291: 
vulnerability analysis and mitigation

CVE-2026-24291, dubbed RegPwn, is a local privilege escalation vulnerability in the Windows Accessibility Infrastructure component (ATBroker.exe) caused by incorrect permission assignment for a critical resource. An authenticated local attacker with low privileges can exploit this flaw to elevate to SYSTEM-level access without requiring user interaction. The vulnerability was disclosed and patched on March 10, 2026, as part of Microsoft's March 2026 Patch Tuesday. It carries a CVSS v3.1 base score of 7.8 (High) (Microsoft MSRC, Feedly).

The root cause is classified as CWE-732 (Incorrect Permission Assignment for Critical Resource), where ATBroker.exe — the Assistive Technology Broker process in Windows Accessibility Infrastructure — has misconfigured permissions on a critical registry resource or object. This misconfiguration allows a low-privileged local user to manipulate the resource in a way that triggers privilege escalation to SYSTEM. The attack vector is local (AV:L), requires low privileges (PR:L), and no user interaction (UI:N), making it straightforward to exploit once local access is obtained. MDSec ActiveBreach published a detailed technical write-up and released public exploit code ("RegPwn") demonstrating the technique, which leverages registry permission weaknesses to hijack a privileged process (MDSec Blog, RegPwn GitHub).

Successful exploitation grants an attacker complete SYSTEM-level control over the affected Windows host, enabling arbitrary code execution, access to all sensitive data on the system, modification of system files, and installation of persistent backdoors. The vulnerability affects a broad range of Windows client and server versions — from Windows 10 1607 and Windows Server 2012 through Windows 11 26H1 and Windows Server 2025 — significantly widening the attack surface across enterprise environments. While the attack is local, it is a critical post-exploitation step enabling lateral movement and full domain compromise when combined with initial access techniques (Microsoft MSRC, MDSec Blog).

1. Gain Local Access: Obtain a low-privileged local user account on a vulnerable Windows system (e.g., via phishing, credential theft, or exploitation of another vulnerability).
2. Identify Target: Confirm the target is running a vulnerable Windows version (Windows 10 1607–22H2, Windows 11 23H2–26H1, or Windows Server 2012–2025) without the March 2026 Patch Tuesday updates applied.
3. Download/Compile RegPwn: Obtain the RegPwn exploit from the MDSec ActiveBreach GitHub repository (https://github.com/mdsecactivebreach/RegPwn), which is written in C# and can be compiled with standard .NET tooling.
4. Exploit Registry Permission Weakness: Execute the compiled RegPwn binary from the low-privileged context. The exploit abuses incorrectly assigned permissions on a registry key associated with ATBroker.exe (Windows Accessibility Infrastructure) to manipulate a critical resource accessible to the privileged process.
5. Hijack Privileged Process: The exploit leverages the misconfigured registry permissions to inject or redirect execution into ATBroker.exe or a related privileged context, achieving code execution as SYSTEM.
6. Achieve SYSTEM Access: Confirm SYSTEM-level shell or process, then proceed with post-exploitation activities such as credential dumping, lateral movement, or persistence installation (MDSec Blog, RegPwn GitHub).

• Process: Unusual child processes spawned by ATBroker.exe (e.g., cmd.exe, powershell.exe) with SYSTEM privileges; unexpected processes running as SYSTEM originating from a low-privileged user session.
• Registry: Unexpected modifications to registry keys under HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Accessibility or related ATBroker registry paths; permission changes on accessibility-related registry keys.
• File System: Presence of RegPwn.exe or similarly named binaries in user-writable directories (e.g., %TEMP%, %APPDATA%); newly created files or scheduled tasks owned by SYSTEM but created from a low-privileged session.
• Logs: Windows Security Event Log entries showing token impersonation (Event ID 4624 with elevated logon type) from a low-privileged account; Event ID 4688 showing ATBroker.exe spawning unexpected child processes; audit logs showing registry key permission changes on accessibility infrastructure keys.
• Network: Outbound connections from ATBroker.exe or newly spawned SYSTEM processes to external IPs (unusual for this process) (MDSec Blog, RegPwn GitHub).

Microsoft released patches on March 10, 2026 as part of Patch Tuesday. Affected systems should be updated to the following minimum build versions: Windows 10 21H2/22H2 → 10.0.19044/19045.7058; Windows 10 1809 → 10.0.17763.8511; Windows 10 1607 → 10.0.14393.8957; Windows 11 23H2 → 10.0.22631.6783; Windows 11 24H2 → 10.0.26100.7979 (or 8037 per ENISA); Windows 11 25H2 → 10.0.26200.7979; Windows 11 26H1 → 10.0.28000.1719; Windows Server 2012/R2 → 6.3.9600.23074; Windows Server 2016 → 10.0.14393.8957; Windows Server 2019 → 10.0.17763.8511; Windows Server 2022 → 10.0.20348.4830; Windows Server 2022 23H2 → 10.0.25398.2207; Windows Server 2025 → 10.0.26100.32463. As a workaround where patching is not immediately possible, restrict local logon rights to minimize the number of users who can execute code on sensitive systems, and implement the principle of least privilege. 0patch also released micropatches for systems that cannot apply the official update (Microsoft MSRC, 0patch Blog).

MDSec ActiveBreach published a detailed blog post titled "RIP RegPwn" alongside the public exploit release, generating significant attention in the security research community on Reddit's r/blueteamsec and social media platforms including Bluesky and LinkedIn. Security vendors including Qualys, Rapid7, Tenable, Sophos, Cisco Talos, and Check Point covered the vulnerability in their March 2026 Patch Tuesday roundups, with several noting the public PoC availability as a key risk factor. KrebsOnSecurity and BleepingComputer also covered the March 2026 Patch Tuesday, highlighting the broader context of the release. The 0patch team later released micropatches, indicating ongoing community interest in supporting systems that cannot immediately apply the official fix (MDSec Blog, 0patch Blog, Qualys Blog).