CVE-2026-62783: Windows 10 Privilege Escalation Flaw

CVE-2026-62783 Overview

CVE-2026-62783 is a heap-based buffer overflow [CWE-122] in the Windows Remote Access Connection Manager (RasMan) service. The flaw allows an authenticated local attacker to corrupt heap memory and elevate privileges on the affected host. Microsoft published the advisory on 2026-08-11, and the vulnerability affects a broad set of supported Windows client and server releases, including Windows 10, Windows 11, and Windows Server 2019 through 2025.

Exploitation requires local access and low-privileged authentication. Successful abuse yields high impact to confidentiality, integrity, and availability, typically resulting in SYSTEM-level code execution.

Critical Impact
A local authenticated attacker can trigger a heap overflow in rasman.dll to escalate from a standard user to SYSTEM, undermining host isolation and enabling full endpoint compromise.

Affected Products

Microsoft Windows 10 (1809, 21H2, 22H2) on x86, x64, and ARM64
Microsoft Windows 11 (23H2, 24H2, 25H2, 26H1) on x64 and ARM64
Microsoft Windows Server 2019, 2022, and 2025

Discovery Timeline

2026-08-11 - CVE-2026-62783 published to NVD
2026-08-13 - Last updated in NVD database

Technical Details for CVE-2026-62783

Vulnerability Analysis

The Remote Access Connection Manager (RasMan) is a Windows service that manages dial-up and virtual private network (VPN) connections. It runs as SYSTEM under svchost.exe and exposes remote procedure call (RPC) interfaces reachable by local low-privileged callers. CVE-2026-62783 exists in the service's handling of connection metadata, where an attacker-controlled input is copied into a heap buffer without adequate size validation.

When the oversized data is written past the allocated chunk boundary, adjacent heap metadata or object pointers are corrupted. A local attacker who has already authenticated to the host can call the vulnerable RasMan interface repeatedly, shape the heap, and hijack control flow inside a SYSTEM process. The result is a reliable local privilege escalation on default installations of Windows 10, Windows 11, and Windows Server.

Root Cause

The root cause is a classic heap-based buffer overflow [CWE-122] in RasMan. The service allocates a fixed-size heap buffer based on assumed input constraints, then copies caller-supplied bytes into it without enforcing the target buffer's actual capacity. This mismatch between allocation size and copy length permits out-of-bounds writes on the process heap.

Attack Vector

The attack vector is local. An adversary must already have code execution as a low-privileged user, for example through a phishing payload, a compromised service account, or an initial-access foothold. From that context, the attacker invokes the vulnerable RasMan RPC path with a crafted request that exceeds the target buffer. No user interaction is required, and exploitation completes within the boundaries of the local host. Verified public exploit code is not currently listed on ExploitDB, and the flaw is not on the CISA Known Exploited Vulnerabilities catalog as of publication.

No verified public proof-of-concept code is available. See the Microsoft Security Update Guide CVE-2026-62783 advisory for vendor-supplied technical details.

Detection Methods for CVE-2026-62783

Indicators of Compromise

Unexpected crashes of svchost.exe instances hosting the RasMan service, especially with Windows Error Reporting entries referencing rasman.dll.
Creation of new local administrator accounts or scheduled tasks immediately after RasMan service anomalies.
Non-administrative processes issuing RPC calls to the RasMan interface followed by child processes running as NT AUTHORITY\SYSTEM.

Detection Strategies

Monitor Windows Event Log IDs 7031, 7034, and 1000 for RasMan service failures and application crashes tied to rasman.dll.
Alert on token-elevation patterns where a low-integrity parent spawns a SYSTEM child process, using Sysmon Event ID 1 with IntegrityLevel deltas.
Correlate RPC endpoint activity (\\pipe\\srvsvc, RasMan endpoints) with subsequent privilege changes on the same host.

Monitoring Recommendations

Enable Windows Defender Exploit Guard and Attack Surface Reduction rules that block credential and LSASS-adjacent process misuse.
Ingest endpoint process, service, and crash telemetry into a centralized SIEM to baseline normal RasMan behavior and flag deviations.
Track patch state for KB updates referenced in the Microsoft Security Update Guide CVE-2026-62783 advisory across all Windows endpoints and servers.

How to Mitigate CVE-2026-62783

Immediate Actions Required

Apply the Microsoft security update for CVE-2026-62783 to all affected Windows 10, Windows 11, and Windows Server systems as documented in the Microsoft Security Update Guide CVE-2026-62783.
Prioritize patching multi-user hosts, jump servers, Remote Desktop hosts, and VDI infrastructure where multiple low-privileged sessions coexist.
Audit local account membership and remove unused interactive logon rights to reduce the pool of accounts that can trigger the flaw.

Patch Information

Microsoft has released security updates addressing CVE-2026-62783 across the affected Windows client and server versions. Consult the Microsoft Security Update Guide CVE-2026-62783 for the exact KB article numbers matching each build. Deploy the updates through Windows Update, Windows Server Update Services (WSUS), Microsoft Intune, or Configuration Manager according to your patch management process.

Workarounds

If patching must be delayed, disable the RasMan service on hosts that do not require dial-up or VPN client functionality: sc.exe config RasMan start= disabled followed by sc.exe stop RasMan.
Restrict interactive and remote interactive logon rights so that only trusted administrators can reach the local RPC surface of RasMan.
Enforce application allowlisting to limit which binaries low-privileged users can execute, reducing the ability to stage exploit tooling.

bash

# Configuration example: disable RasMan where VPN/dial-up is not required
sc.exe stop RasMan
sc.exe config RasMan start= disabled