CVE-2025-49604 is a medium-severity heap-based buffer overflow vulnerability affecting Realtek AmebaD devices, specifically in the WLAN driver defragmentation function. The vulnerability exists in the Ameba-AIoT ameba-arduino-d firmware versions prior to 3.1.9 and ameba-rtos-d versions before commit c2bfd8216a1cbc19ad2ab5f48f372ecea756d67a, disclosed on July 3, 2025. The root cause is the lack of validation of the size of fragmented Wi-Fi frames during the defragmentation process. When fragmented Wi-Fi frames are processed, the driver fails to properly check the size before copying data into a heap buffer, which can lead to a heap-based buffer overflow (CWE-122). This type of overflow can corrupt adjacent memory, potentially allowing an attacker to execute arbitrary code or cause denial of service by crashing the device. The CVSS v3.1 base score is 5.4, indicating a medium severity, with an attack vector of network (AV:N), low attack complexity (AC:L), requiring low privileges (PR:L), no user interaction (UI:N), unchanged scope (S:U), and limited impact on confidentiality and integrity (C:L/I:L) but no impact on availability (A:N). No known exploits are currently reported in the wild, and no official patches or updates have been linked yet. The vulnerability affects IoT devices using Realtek AmebaD chipsets, which are commonly embedded in various smart devices and industrial IoT applications. Because the vulnerability is exploitable remotely over the network without user interaction, it poses a risk for attackers to compromise affected devices within wireless range or connected networks. However, exploitation requires at least low privileges, which may limit the attack surface somewhat.

For European organizations, the impact of this vulnerability depends largely on the deployment of Realtek AmebaD-based IoT devices within their infrastructure. Industries such as manufacturing, smart building management, healthcare, and critical infrastructure that utilize IoT sensors, controllers, or wireless devices with these chipsets could face risks of device compromise or disruption. Successful exploitation could lead to unauthorized access to device memory, potentially allowing attackers to manipulate device behavior, exfiltrate sensitive data, or disrupt operations. Given the medium severity and the requirement for low privileges, attackers might leverage this vulnerability as a foothold within internal networks or to pivot to other systems. The lack of user interaction and network-based attack vector increases the risk in environments with wireless connectivity. European organizations with extensive IoT deployments should be particularly vigilant, as compromised devices could undermine operational technology security and data integrity. However, the absence of known exploits in the wild and the medium CVSS score suggest the immediate risk is moderate but warrants proactive mitigation.

1. Inventory and identify all devices using Realtek AmebaD chipsets within the organization’s network, especially those running Ameba-AIoT ameba-arduino-d firmware versions prior to 3.1.9 or ameba-rtos-d before the specified commit. 2. Monitor vendor communications and security advisories for official patches or firmware updates addressing CVE-2025-49604 and apply them promptly once available. 3. Implement network segmentation to isolate IoT devices from critical IT infrastructure, limiting potential lateral movement in case of compromise. 4. Restrict wireless access to IoT devices by enforcing strong Wi-Fi security protocols, using WPA3 where possible, and limiting device connectivity to trusted networks. 5. Employ intrusion detection systems (IDS) and anomaly detection tools tuned to detect unusual Wi-Fi frame fragmentation or malformed packets that could indicate exploitation attempts. 6. Regularly audit and update device firmware to the latest secure versions, and consider disabling unnecessary wireless features or services on IoT devices to reduce attack surface. 7. For devices that cannot be updated immediately, consider temporary compensating controls such as reducing wireless signal range or employing physical security controls to limit attacker proximity.