CVE-2026-42904: Windows TCP/IP Elevation of Privilege Vulnerability

Synopsis

Heap-based buffer overflow in the Windows TCP/IP stack affects multiple versions of Windows 10, Windows 11, and Windows Server 2022. An attacker on the same network segment (LAN, VPN, or adjacent subnet) can trigger the overflow without any credentials or victim interaction, gaining elevated privileges on the target system. Successful exploitation gives the attacker full control over confidentiality, integrity, and availability of the affected host, with scope extending beyond the vulnerable component. Patched-image rebuilds at the fix versions listed above are available on HarborGuard for environments running affected Windows-based container images.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityDetail

  The attacker must be on an adjacent network segment (local network, VPN, or shared subnet); the vulnerability is not reachable from the open internet without that adjacency.

• AuthenticationNot required

  No credentials or account of any kind are needed; the attacker sends malformed TCP/IP traffic without authenticating to the target.

• Victim interactionNot required

  The target does not need to open a file, click a link, or take any action for exploitation to succeed.

• Attack complexityDetail

  The exploit is reliable and requires no special preconditions, race conditions, or knowledge of memory layout; any attacker with network adjacency can attempt it consistently.

Blast Radius

• A successful attacker elevates from an unprivileged adjacent-network position to a privileged execution context on the target host.
• All data accessible to the compromised TCP/IP process is exposed, including network traffic, credentials cached in memory, and configuration secrets.
• The attacker gains write access to system state, enabling modification of routing tables, firewall rules, or persisted files on the host.
• The scope extends beyond the vulnerable component itself, meaning an attacker can affect other processes and resources on the same host, including container management layers.