CVE-2025-3854 is a buffer overflow vulnerability identified in the H3C GR-3000AX router, specifically affecting firmware versions up to V100R006. The vulnerability resides within the HTTP POST request handler component, impacting several functions including EnableIpv6, UpdateWanModeMulti, UpdateIpv6Params, EditWlanMacList, and Edit_List_SSID located in the /goform/aspForm endpoint. The root cause is the improper handling of the 'param' argument, which allows an attacker to overflow the buffer by sending crafted HTTP POST requests. This memory corruption can lead to arbitrary code execution or denial of service on the device. Exploitation requires the attacker to be within the local network, as the vulnerable functions are accessible only through local HTTP POST requests. Although the vulnerability is classified as critical by the vendor, the published severity is medium, possibly reflecting the local network access requirement and lack of known exploits in the wild. The disclosure is public, and while no patches or exploits have been reported yet, other functions within the same component may also be vulnerable, indicating a broader attack surface. The vulnerability affects a widely deployed enterprise-grade router model, which is often used in small to medium business environments and possibly in some enterprise network segments.

For European organizations, the exploitation of this vulnerability could result in significant security risks. Successful exploitation can lead to unauthorized control over the affected router, enabling attackers to intercept, modify, or disrupt network traffic, potentially compromising confidentiality and integrity of sensitive data. Additionally, attackers could disrupt network availability by causing device crashes or reboots. Given that the attack requires local network access, the threat is particularly relevant for organizations with insufficient internal network segmentation or weak access controls. The impact is heightened in environments where the H3C GR-3000AX is deployed as a critical network gateway or in branch offices with less stringent security monitoring. Compromise of such devices could facilitate lateral movement within the network, leading to broader organizational exposure. Furthermore, the lack of available patches at the time of disclosure increases the window of vulnerability, necessitating immediate mitigation efforts to prevent exploitation.

Organizations should immediately identify and inventory all H3C GR-3000AX devices running firmware versions up to V100R006. Until an official patch is released, it is recommended to implement strict network segmentation to isolate these devices from untrusted or less secure network segments, limiting local network access to trusted administrators only. Employ access control lists (ACLs) to restrict HTTP management interfaces to specific IP addresses or VLANs. Disable remote management features if enabled, and enforce strong authentication mechanisms for device access. Continuous monitoring of network traffic for unusual POST requests targeting /goform/aspForm endpoints can help detect exploitation attempts. Additionally, organizations should engage with H3C support channels to obtain firmware updates or workarounds as soon as they become available. Regularly updating device firmware and applying security advisories promptly will reduce exposure to this and similar vulnerabilities. Finally, conducting internal penetration testing focusing on local network threats can help identify and remediate potential attack vectors related to this vulnerability.