CVE-2024-21344 Overview
CVE-2024-21344 is a denial of service vulnerability in the Windows Network Address Translation (NAT) component. A remote attacker can send crafted network traffic to a vulnerable Windows host performing NAT, causing service disruption. The flaw is associated with an out-of-bounds read condition [CWE-125] in NAT processing logic.
Microsoft addressed the issue in the February 2024 Patch Tuesday release. The vulnerability affects a broad range of Windows client and server versions that provide NAT functionality, including Internet Connection Sharing and Routing and Remote Access Service (RRAS) roles.
Critical Impact
Successful exploitation causes the NAT service to fail, disrupting network connectivity for downstream clients that rely on the affected host for translation and routing.
Affected Products
- Microsoft Windows 10 (versions 1507, 1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (versions 21H2, 22H2, 23H2)
- Microsoft Windows Server 2012 R2, 2016, 2019, 2022, and 2022 23H2
Discovery Timeline
- 2024-02-13 - CVE-2024-21344 published to NVD and Microsoft security update released
- 2026-08-10 - Last updated in NVD database
Technical Details for CVE-2024-21344
Vulnerability Analysis
The vulnerability resides in the Windows NAT driver, which translates internal IP addresses and ports to external ones for connections traversing the host. NAT processing occurs in kernel-mode components that parse untrusted packet fields such as IP headers, transport-layer headers, and application-layer identifiers used by supported NAT helpers.
When the NAT engine parses a malformed packet, it reads memory beyond the intended packet boundary [CWE-125]. The out-of-bounds read triggers a fault in kernel-mode code, halting NAT operations and dropping traffic for clients that depend on the translation service.
Attack complexity is high because the attacker must win specific timing or state conditions and craft packets that reach the vulnerable parsing path. The vulnerability does not require authentication or user interaction, and impacts availability only.
Root Cause
The root cause is missing or insufficient bounds validation when the NAT component parses fields from inbound network packets. Undersized or truncated packets that pass initial length checks can still cause the parser to dereference memory past the end of the buffer, producing an out-of-bounds read [CWE-125] that terminates the processing thread or destabilizes the NAT service.
Attack Vector
Exploitation is network-based. An unauthenticated attacker sends a specifically crafted sequence of packets to a Windows host performing NAT, such as a server running RRAS or a workstation with Internet Connection Sharing enabled. The malformed traffic must reach the NAT parsing path, and the attacker must satisfy race or state conditions that make the flaw reachable. No verified public proof-of-concept code is available.
Detection Methods for CVE-2024-21344
Indicators of Compromise
- Unexpected termination or restart of the Windows NAT driver, RRAS service, or Internet Connection Sharing service on affected hosts.
- Sudden loss of connectivity for clients behind a Windows NAT gateway, accompanied by kernel or system event log entries referencing NAT components.
- Bursts of malformed or truncated packets destined for the external interface of a NAT host from a single or small set of remote sources.
Detection Strategies
- Correlate Windows event log entries for RRAS or NAT service failures with concurrent inbound traffic anomalies at the network edge.
- Deploy IDS/IPS signatures that flag malformed packets targeting NAT translation paths, focusing on protocol fields with abnormal length values.
- Monitor kernel crash dumps and Windows Error Reporting telemetry for faults in NAT-related drivers following network events.
Monitoring Recommendations
- Track availability metrics for services provided through Windows NAT gateways and alert on abrupt drops that coincide with external traffic spikes.
- Enable and centralize System and Application event logs from all Windows hosts running RRAS or Internet Connection Sharing.
- Baseline normal inbound protocol distributions to affected hosts so that anomalous packet patterns targeting NAT are detected quickly.
How to Mitigate CVE-2024-21344
Immediate Actions Required
- Apply the February 2024 Microsoft security update for all affected Windows client and server versions as documented in the Microsoft CVE-2024-21344 Update Guide.
- Inventory hosts running RRAS, Internet Connection Sharing, or other NAT roles and prioritize patching for internet-exposed systems.
- Restrict inbound traffic to NAT hosts to expected sources and protocols using upstream firewall or ACL policies.
Patch Information
Microsoft published fixes for CVE-2024-21344 in the February 13, 2024 security update cycle. Refer to the Microsoft CVE-2024-21344 Update Guide for the specific KB articles applicable to each Windows version and installation path.
Workarounds
- Disable the Routing and Remote Access Service or Internet Connection Sharing on hosts where NAT functionality is not required.
- Place vulnerable NAT hosts behind an upstream firewall that filters malformed or unexpected traffic before it reaches the Windows NAT engine.
- Where feasible, migrate NAT responsibilities to dedicated network appliances until patches are deployed on all Windows systems.
# Example: disable Routing and Remote Access on a Windows Server where NAT is not needed
sc.exe config RemoteAccess start= disabled
sc.exe stop RemoteAccess
# Example: disable Internet Connection Sharing service
sc.exe config SharedAccess start= disabled
sc.exe stop SharedAccess
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
