CVE-2024-21416: Windows 10 1809 TCP/IP RCE Vulnerability

CVE-2024-21416 Overview

CVE-2024-21416 is a remote code execution vulnerability in the Windows TCP/IP networking stack. The flaw affects supported releases of Windows 10, Windows 11, and Windows Server, including Server 2019, Server 2022, and Server 2022 23H2. Microsoft assigned the issue a CVSS 3.1 score of 9.8 and classified it under [CWE-122] heap-based buffer overflow. Exploitation requires no authentication and no user interaction, and the attack vector is network-based. A successful attacker can execute arbitrary code in the context of the Windows kernel networking components.

Critical Impact
Unauthenticated network attackers can trigger memory corruption in the Windows TCP/IP stack and achieve remote code execution on default Windows configurations.

Affected Products

Microsoft Windows 10 (1809, 21H2, 22H2)
Microsoft Windows 11 (21H2, 22H2, 23H2, 24H2)
Microsoft Windows Server 2019, Server 2022, and Server 2022 23H2

Discovery Timeline

2024-09-10 - CVE-2024-21416 published to NVD and addressed in Microsoft's September 2024 Patch Tuesday
2024-09-20 - Last updated in the NVD database

Technical Details for CVE-2024-21416

Vulnerability Analysis

The vulnerability resides in the Windows TCP/IP networking stack, which processes inbound IPv4 and IPv6 packets at the kernel level. Microsoft categorizes the weakness as a heap-based buffer overflow [CWE-122]. An attacker who reaches the target over the network can send specially crafted packets that cause the stack to write beyond an allocated heap buffer. Because the affected code runs in kernel context, successful corruption can lead to arbitrary code execution with SYSTEM privileges.

The issue does not require authentication, user interaction, or prior access to the target. Any Windows host exposing its IP stack to an attacker-controlled network path is in scope, including domain controllers, file servers, and workstations. The combination of network reachability and kernel-level impact makes the vulnerability wormable in theory, though Microsoft and CISA have not reported in-the-wild exploitation. EPSS data places the probability of exploitation activity in the upper percentile range for unpatched flaws.

Root Cause

The root cause is improper validation of size or boundary conditions when the TCP/IP driver parses incoming packet fields. The flawed code path allocates a heap buffer based on assumed packet structure, then copies attacker-influenced data without enforcing the allocated bounds. This produces an out-of-bounds write on the kernel pool. Microsoft has not published the affected function names or offsets in its public advisory.

Attack Vector

Attackers exploit the issue by sending malicious IP packets to a reachable Windows host. No credentials, listening application, or user action are required. Any Windows endpoint reachable over the local network, a VPN, or the public internet through exposed services is a candidate target. The vulnerability is described in the Microsoft Security Update Guide entry for CVE-2024-21416.

No verified public proof-of-concept code is available for CVE-2024-21416 at the time of writing. Technical specifics of the malformed packet structure have not been disclosed by Microsoft.

Detection Methods for CVE-2024-21416

Indicators of Compromise

Unexpected kernel crashes, bug checks, or tcpip.sys-related stop errors on Windows hosts, which may indicate failed exploitation attempts.
Anomalous inbound IPv4 or IPv6 traffic with malformed headers, unusual fragmentation, or invalid option fields targeting Windows hosts.
New kernel-mode processes, drivers, or services appearing immediately after suspicious network activity from external sources.

Detection Strategies

Monitor Windows Event Log entries from Microsoft-Windows-Kernel-General and Microsoft-Windows-TCPIP for repeated faults or driver errors.
Deploy network IDS signatures that flag malformed IPv4 or IPv6 packets, oversized headers, and abnormal TCP option sequences directed at Windows hosts.
Baseline normal inbound packet patterns on perimeter and internal segments, then alert on deviations targeting Windows Server roles such as RDP gateways and domain controllers.

Monitoring Recommendations

Continuously collect kernel telemetry and crash dumps from Windows endpoints and forward them to a centralized SIEM or data lake for correlation.
Track external-to-internal traffic to Windows hosts on all protocols, not just well-known service ports, since the vulnerability is in the IP stack itself.
Prioritize alerting on internet-facing Windows systems and any host that participates in IPv6 transition technologies such as ISATAP or Teredo.

How to Mitigate CVE-2024-21416

Immediate Actions Required

Apply the September 2024 Microsoft security updates to all supported Windows 10, Windows 11, and Windows Server systems listed in the advisory.
Inventory internet-exposed Windows hosts and prioritize patching for systems reachable from untrusted networks.
Validate that automated patching successfully delivered the update by confirming installed KB identifiers against Microsoft's advisory for each affected build.

Patch Information

Microsoft released cumulative updates that remediate CVE-2024-21416 as part of the September 10, 2024 Patch Tuesday release. The fix applies to all supported branches of Windows 10, Windows 11, Windows Server 2019, Windows Server 2022, and Windows Server 2022 23H2. Refer to the Microsoft Security Update Guide for per-build KB article numbers and download links.

Workarounds

Restrict inbound IPv4 and IPv6 traffic at the network perimeter and host firewall to only trusted sources where business requirements allow.
Disable IPv6 transition technologies (Teredo, 6to4, ISATAP) on systems that do not require them to reduce the exposed attack surface.
Segment vulnerable hosts away from untrusted networks until the September 2024 update can be applied.

bash

# Example: disable IPv6 transition technologies as a temporary hardening step
netsh interface teredo set state disabled
netsh interface 6to4 set state disabled
netsh interface isatap set state disabled