EUVD-2026-56396
GHSA-v63m-ccr7-h559
Severity by source
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
RRAS is network-accessible with authentication bypass (PR:N, AV:N), but UAF exploitation requires heap control or race condition (AC:H); full RCE yields C:H/I:H/A:H with no scope change.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Remote Code Execution in Windows Routing and Remote Access Service (RRAS) allows attacker to gain an unauthorized access to victim's machine
AnalysisAI
Remote code execution in Windows Routing and Remote Access Service (RRAS) allows unauthenticated network attackers to fully compromise affected hosts across an exceptionally broad range of Windows versions, from Server 2012 through Server 2025 and Windows 10/11. The root cause is a use-after-free memory corruption flaw (CWE-416) combined with an authentication bypass, enabling an attacker to execute arbitrary code without credentials. No public exploit code or CISA KEV listing has been identified at time of analysis, but the network-exposed attack surface, zero-authentication barrier, and breadth of affected platforms make this a high-priority patching target. A vendor-released patch is available via Microsoft MSRC.
Technical ContextAI
Windows RRAS is a built-in Windows Server component providing VPN gateway, dial-up routing, and network address translation (NAT) services. It handles inbound network protocol traffic including PPTP (TCP/1723), IKEv2 (UDP/500, UDP/4500), and SSTP (TCP/443). The root cause is CWE-416 (Use-After-Free): a freed memory object in the RRAS protocol handler is subsequently accessed, creating a memory corruption condition. UAF bugs in network-accessible services are particularly dangerous because they can be triggered by crafted packets and may allow precise control over freed memory regions through heap-spray or object reuse techniques. The CVSS vector (AV:N/AC:H/PR:N/UI:N) confirms the service is reachable over the network without credentials, while AC:H indicates exploitation requires navigating specific protocol state, memory layout, or timing conditions - consistent with reliable UAF exploitation complexity. The 'Authentication Bypass' tag in EUVD-2026-56396 data suggests the memory corruption itself circumvents normal credential validation. Affected CPE data from ENISA EUVD covers Windows Server 2012 through 2025 and Windows 10/11 consumer editions.
RemediationAI
Apply the Microsoft security update corresponding to your Windows version using the patched build numbers provided in ENISA EUVD-2026-56396 and confirmed via the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62819. Target build numbers are: Server 2012 to 6.2.9200.26279, Server 2012 R2 to 6.3.9600.23337, Server 2016 and Windows 10 1607 to 10.0.14393.9418, Server 2019 and Windows 10 1809 to 10.0.17763.9115, Server 2022 to 10.0.20348.5499, Server 2025 and Windows 11 24H2 to 10.0.26100.9168 or 10.0.26100.33296 respectively, Windows 10 21H2 to 10.0.19044.7663, Windows 10 22H2 to 10.0.19045.7663, Windows 11 23H2 to 10.0.22631.7517, Windows 11 25H2 to 10.0.26200.9168, and Windows 11 26H1 to 10.0.28000.2704. If patching is not immediately feasible, disable the RemoteAccess (RRAS) service on any system that does not actively require VPN or routing functionality via 'Set-Service RemoteAccess -StartupType Disabled; Stop-Service RemoteAccess' - note this immediately terminates all VPN and routing sessions. For hosts that must run RRAS, restrict inbound RRAS protocol ports (TCP/1723 PPTP, UDP/500 and UDP/4500 IKEv2, TCP/443 SSTP) to known trusted IP ranges using Windows Firewall Advanced Security or perimeter network controls; this reduces exposure but does not eliminate risk if trusted ranges include attacker-reachable systems.
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Same weakness CWE-416 – Use After Free
View allSame technique Authentication Bypass
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External POC / Exploit Code
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