CVE-2026-57096 Overview
CVE-2026-57096 is a heap-based buffer overflow vulnerability [CWE-122] in the Windows Routing and Remote Access Service (RRAS). An authorized local attacker can exploit this flaw to elevate privileges on affected systems. The vulnerability spans nearly every currently supported Windows client and server release, including Windows 10, Windows 11 (24H2, 25H2, 26H1), and Windows Server 2012 through 2025.
Microsoft published the advisory on July 14, 2026. Successful exploitation grants attackers high impact on confidentiality, integrity, and availability, effectively enabling full system compromise from a low-privileged local account.
Critical Impact
A low-privileged local user can trigger a heap overflow in RRAS to gain SYSTEM-level privileges across all supported Windows versions.
Affected Products
- Microsoft Windows 10 (1607, 1809, 21H2, 22H2) on x86, x64, and ARM64
- Microsoft Windows 11 (24H2, 25H2, 26H1) on x64 and ARM64
- Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025
Discovery Timeline
- 2026-07-14 - CVE CVE-2026-57096 published to NVD
- 2026-07-14 - Microsoft releases security update addressing CVE-2026-57096
- 2026-07-20 - Last updated in NVD database
Technical Details for CVE-2026-57096
Vulnerability Analysis
The vulnerability resides in the Windows Routing and Remote Access Service (RRAS), a Windows role that supports VPN, dial-up, and site-to-site routing. RRAS runs with elevated privileges and exposes local RPC interfaces used by administrative and management tooling. A malformed request to one of these interfaces triggers an out-of-bounds write on the heap.
Because RRAS handles the crafted input inside a privileged process, corrupted heap memory can be leveraged to redirect execution flow. Attackers can chain the overflow with standard heap grooming techniques to achieve arbitrary code execution in the RRAS service context.
The CWE-122 classification confirms that the root defect is a heap-based buffer overflow rather than a stack or integer boundary issue. Exploitation requires local access and a valid authenticated session but no user interaction.
Root Cause
The root cause is improper validation of the size of attacker-controlled input before it is copied into a heap-allocated buffer inside an RRAS routine. When the input exceeds the allocated chunk, adjacent heap metadata or function pointers become corruptible. Microsoft has not published detailed technical internals in the advisory.
Attack Vector
The attack vector is local. An authorized attacker sends a specially crafted request through an RRAS-exposed local interface. The malformed payload triggers the overflow inside the privileged service and allows the attacker to execute code as SYSTEM.
No verified public exploit code is available. See the Microsoft Security Update CVE-2026-57096 advisory for vendor guidance.
Detection Methods for CVE-2026-57096
Indicators of Compromise
- Unexpected crashes, restarts, or Windows Error Reporting entries associated with the RemoteAccess service or svchost.exe hosting RRAS.
- Creation of new services, scheduled tasks, or local administrator accounts shortly after RRAS process anomalies.
- Child processes spawned by the RRAS service host that are not part of normal administrative workflows.
Detection Strategies
- Hunt for anomalous process lineage where the RRAS service host launches interactive shells such as cmd.exe, powershell.exe, or rundll32.exe.
- Correlate RRAS service crashes with subsequent privilege changes or token manipulation events in the same session.
- Alert on heap corruption or exception events in the RRAS service in Windows Event Log and application crash telemetry.
Monitoring Recommendations
- Enable command-line and process-creation auditing (Event ID 4688) on all servers running the Routing and Remote Access role.
- Monitor changes to RRAS configuration keys under HKLM\SYSTEM\CurrentControlSet\Services\RemoteAccess.
- Baseline expected RRAS activity so that unexpected RPC clients invoking RRAS interfaces are flagged for review.
How to Mitigate CVE-2026-57096
Immediate Actions Required
- Apply the July 2026 Microsoft security update referenced in the Microsoft Security Update CVE-2026-57096 advisory to all affected Windows client and server systems.
- Inventory systems with the Routing and Remote Access role enabled and prioritize patching for internet-adjacent gateways and VPN concentrators.
- Restrict local logon rights on RRAS-hosting servers to reduce the pool of accounts that satisfy the local access precondition.
Patch Information
Microsoft has published fixes for all affected Windows versions through the standard security update channel. Refer to the Microsoft Security Update CVE-2026-57096 advisory for the specific KB article and build numbers that apply to each supported release.
Workarounds
- Disable the Routing and Remote Access service on systems that do not require VPN or routing functionality.
- Enforce least privilege on servers running RRAS and remove unnecessary interactive or Remote Desktop access.
- Segment RRAS servers on isolated management networks to limit adversary pivoting after any successful local privilege escalation.
# Disable the RRAS service on hosts that do not require it (PowerShell, run as Administrator)
Stop-Service -Name RemoteAccess -Force
Set-Service -Name RemoteAccess -StartupType Disabled
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
