CVE-2026-62819 Overview
CVE-2026-62819 is a remote code execution vulnerability in the Windows Routing and Remote Access Service (RRAS). The flaw stems from a use-after-free condition [CWE-416] in the RRAS component. An unauthenticated attacker can exploit this weakness over the network to gain unauthorized access to a target system. Microsoft published the advisory on 2026-08-11 and last updated it on 2026-08-12.
Successful exploitation compromises confidentiality, integrity, and availability of the affected host. The high attack complexity requires the attacker to win a race or manipulate memory state, which reduces the likelihood of trivial mass exploitation.
Critical Impact
Unauthenticated network attackers who successfully exploit the use-after-free condition in RRAS can execute arbitrary code on the target system and take full control of the host.
Affected Products
- Microsoft Windows systems with the Routing and Remote Access Service (RRAS) role enabled
- Refer to the Microsoft Security Response Center advisory for the complete list of affected Windows builds
Discovery Timeline
- 2026-08-11 - CVE-2026-62819 published to NVD
- 2026-08-12 - Last updated in NVD database
Technical Details for CVE-2026-62819
Vulnerability Analysis
The vulnerability is a use-after-free defect [CWE-416] in the Windows Routing and Remote Access Service. RRAS handles routing, VPN, and dial-up networking on Windows Server systems. When RRAS processes crafted network requests, it references memory that has already been freed. An attacker who controls the reallocation of that memory region can hijack execution flow.
Exploitation requires no authentication and no user interaction. However, the attack complexity is high, indicating that the attacker must win a race condition or satisfy specific memory-layout preconditions. The EPSS score of 0.592% reflects the barrier to reliable weaponization at the time of publication.
Root Cause
The root cause is improper memory lifetime management inside an RRAS request-handling code path. A pointer continues to reference an object after that object has been freed. Subsequent operations dereference the stale pointer, allowing an attacker who reclaims the freed allocation to control fields used by RRAS.
Attack Vector
The attack vector is the network. An attacker sends crafted packets or requests to an internet-reachable or internally reachable RRAS endpoint. By triggering the free and then reallocating the region with attacker-controlled data, the adversary corrupts function pointers or object metadata. This leads to arbitrary code execution in the context of the RRAS service, typically SYSTEM.
No public proof-of-concept code has been published. Microsoft has not confirmed exploitation in the wild, and CISA has not added this CVE to the Known Exploited Vulnerabilities catalog. Refer to the Microsoft advisory for technical guidance.
Detection Methods for CVE-2026-62819
Indicators of Compromise
- Unexpected crashes, restarts, or access violations in the RemoteAccess or RasMan service processes
- Anomalous inbound network traffic to RRAS-related ports such as TCP/1723 (PPTP), UDP/500 and UDP/4500 (IKE/IPsec), and protocol 47 (GRE)
- New or unexpected child processes spawned by RRAS service binaries
- Outbound network connections initiated by RRAS host processes to untrusted destinations
Detection Strategies
- Monitor Windows Event Log for service crash entries (Event ID 7031, 7034) referencing RRAS components
- Alert on suspicious process creation lineage where SYSTEM-level RRAS binaries spawn shells, scripting hosts, or LOLBins
- Inspect network flow telemetry for malformed or high-volume RRAS protocol traffic from untrusted sources
Monitoring Recommendations
- Enable verbose logging on RRAS servers and forward events to a centralized SIEM for correlation
- Baseline normal RRAS traffic patterns and alert on deviations in packet size, flags, and source distribution
- Track patch state across all Windows Server hosts running the RRAS role to identify unpatched systems
How to Mitigate CVE-2026-62819
Immediate Actions Required
- Apply the security update referenced in the Microsoft CVE-2026-62819 advisory to all Windows Server hosts running RRAS
- Inventory every system with the Routing and Remote Access role enabled and prioritize internet-exposed hosts
- Restrict inbound access to RRAS listeners using host and perimeter firewalls until patches are validated
Patch Information
Microsoft has released an official security update addressing the use-after-free condition in RRAS. Administrators should consult the Microsoft Security Response Center guidance for the specific KB article and build numbers that apply to each affected Windows version.
Workarounds
- Disable the Routing and Remote Access Service on systems that do not require it
- Block RRAS-associated ports (TCP/1723, UDP/500, UDP/4500, GRE protocol 47) at the perimeter for untrusted networks
- Place RRAS endpoints behind VPN concentrators or reverse proxies that terminate untrusted traffic
# Check RRAS service status and disable if not required
sc.exe query RemoteAccess
sc.exe config RemoteAccess start= disabled
sc.exe stop RemoteAccess
# Block RRAS-related ports at the Windows firewall
netsh advfirewall firewall add rule name="Block PPTP Inbound" dir=in action=block protocol=TCP localport=1723
netsh advfirewall firewall add rule name="Block IKE Inbound" dir=in action=block protocol=UDP localport=500
netsh advfirewall firewall add rule name="Block IPsec NAT-T Inbound" dir=in action=block protocol=UDP localport=4500
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
