Executive brief
FreeRTOS-Plus-TCP is a networking library used by embedded devices to connect to the internet and local networks. A flaw in how the library processes network configuration messages (DHCPv6) allows an attacker on the same local network to crash the device or corrupt its network settings. This could lead to a total loss of connectivity for the device, requiring a physical hardware reset to restore service.
Technical details
An integer underflow vulnerability exists within the DHCPv6 sub-option parsing logic of the FreeRTOS-Plus-TCP stack. An attacker located on the same local network (adjacent) can send specially crafted DHCPv6 packets to trigger the underflow. This results in the corruption of critical network parameters, including IPv6 address assignments, DNS configurations, and lease times. Furthermore, the exploit can cause the IP task to freeze, leading to a permanent denial of service that necessitates a hardware reset. The issue is resolved in versions V4.4.1 and V4.2.6; a workaround involves disabling DHCPv6 via the ipconfigUSE_DHCPv6 configuration flag.
Affected products
- Amazon Web Services FreeRTOS-Plus-TCP >=V4.0.0, <=V4.2.5; >=V4.3.0, <= V4.4.0
Timeline
- 2026-04-29: disclosed
- 2026-04-29: patched: Fixed in versions V4.4.1 and V4.2.6