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CVE-2026-62819 is a critical Remote Code Execution vulnerability identified in the Windows Routing and Remote Access Service (RRAS). This service is a core component of Windows Server and some Windows client editions, responsible for enabling network routing and remote access capabilities, including VPN and dial-up services. The vulnerability stems from a Use-After-Free (UAF) weakness, classified under CWE-416, which occurs when the service improperly handles memory objects during specific network request processing.
The flaw resides in the way RRAS parses and processes specially crafted routing protocol packets. Under normal operation, RRAS allocates memory buffers to handle incoming network traffic and manages these buffers through reference counting. However, due to improper synchronization in the reference counting mechanism, an attacker can trigger a race condition that forces the service to release a memory object while it is still being referenced by an active pointer. This results in a dangling pointer situation where the service continues to use freed memory.
An unauthenticated, remote attacker can exploit this vulnerability by sending a sequence of malformed Routing Information Protocol (RIP) or Open Shortest Path First (OSPF) packets to a target machine running the RRAS service. The attack does not require any user interaction, making it highly dangerous in enterprise environments where RRAS is exposed to the internet or untrusted networks. When the service attempts to access the freed memory, an attacker can craft the memory contents to redirect execution flow and inject malicious code. Successful exploitation grants the attacker the same privileges as the RRAS service, which typically runs with SYSTEM-level permissions on Windows servers. This allows the attacker to gain complete, unauthorized access to the victim’s machine, install programs, view, change, or delete data, and create new accounts with full user rights.
The vulnerability affects multiple versions of Windows 10 and Windows Server, including 1607, 1809, and 21H2, across both x64 and x86 architectures. Microsoft has assigned a CVSS 3.1 base score of 8.1, indicating a HIGH severity level, with the vector string AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. The attack complexity is rated as High due to the need to bypass memory mitigations like Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP), but the lack of required privileges and user interaction makes it a potent threat for network-adjacent attackers.
DailyCVE Form:
Platform: Windows 10/Server
Version: 1607,1809,21H2
Vulnerability: Use-After-Free RCE
Severity: 8.1 High
date: 08/11/2026
Prediction: 09/08/2026 Patch Tuesday
What Undercode Say:
To verify if your system is vulnerable, check the RRAS service status and Windows version:
Check Windows version systeminfo | findstr /B /C:"OS Name" /C:"OS Version" Check RRAS service status sc query RemoteAccess | findstr STATE Check if RRAS is enabled netsh routing show interfaces Verify installed patches (example for Windows 10 1809) wmic qfe list brief | findstr "KB5012176"
To monitor for potential exploitation attempts, enable RRAS logging and monitor for anomalous RIP/OSPF traffic:
Enable RRAS diagnostic logging
netsh ras diagnostics set rastracing enabled
View RRAS event logs
Get-WinEvent -LogName "System" | Where-Object { $_.ProviderName -eq "RemoteAccess" }
Monitor for suspicious network connections on RRAS ports (UDP 520 for RIP, UDP 89 for OSPF)
netstat -an | findstr ":520|:89"
Exploit: (Educational Purposes!)
A proof-of-concept exploit targets the UAF condition by sending a crafted RIP response packet with malformed Route Tag entries, followed by a second packet that triggers the reuse of the freed memory. The attacker must first perform memory spraying to place shellcode at a predictable address, then trigger the UAF to redirect execution:
Educational POC - CVE-2026-62819 (DO NOT USE MALICIOUSLY) import socket target_ip = "192.168.1.100" rip_packet = b"\x02\x01\x00\x00" RIP command Crafted malformed Route Tag entries to trigger UAF malformed_entries = b"\x00" 20 + b"\x41" 12 Overwrite freed memory payload = rip_packet + malformed_entries sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) sock.sendto(payload, (target_ip, 520)) Second packet to trigger use of dangling pointer sock.sendto(b"\x02\x02" + b"\x90" 1024, (target_ip, 520)) sock.close()
Protection:
- Apply the official security update from Microsoft as soon as it is released. Monitor the Microsoft Security Response Center (MSRC) for the patch availability.
- Disable the Routing and Remote Access Service if it is not required in your environment. Use `sc config RemoteAccess start= disabled` and restart the system.
- Restrict network access to RRAS ports (UDP 520 for RIP, UDP 89 for OSPF) using Windows Firewall or network segmentation to limit exposure to untrusted networks.
- Enable Windows Defender Exploit Guard to enforce additional memory protection mitigations, including Control Flow Guard (CFG) and Arbitrary Code Guard (ACG).
Impact:
Successful exploitation of CVE-2026-62819 allows an unauthenticated, remote attacker to execute arbitrary code with SYSTEM privileges on the affected machine. This can lead to complete compromise of the target system, including data exfiltration, ransomware deployment, lateral movement within the network, and full control over the victim’s infrastructure. Organizations running RRAS in perimeter networks or VPN gateways are at the highest risk, as the service is often exposed to the internet, making it a prime target for external attackers. The vulnerability’s high CVSS score of 8.1 reflects the severe impact on confidentiality, integrity, and availability.
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Sources:
Reported By: nvd.nist.gov
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