CVE-2026-2329 is a stack-based buffer overflow vulnerability classified under CWE-121, found in the HTTP API endpoint /cgi-bin/api.values.get of Grandstream GXP1610 series VoIP phones, including models GXP1610, GXP1615, GXP1620, GXP1625, GXP1628, and GXP1630. This vulnerability allows a remote attacker to send specially crafted HTTP requests to the affected endpoint without any authentication or user interaction, triggering a buffer overflow that can lead to arbitrary code execution with root privileges on the device. The vulnerability impacts the device's confidentiality, integrity, and availability by enabling full system compromise, potentially allowing attackers to intercept calls, manipulate device configurations, or use the device as a foothold for lateral movement within a network. The CVSS 4.0 score of 9.3 reflects the vulnerability's critical nature, with network attack vector, no required privileges or user interaction, and high impact on all security properties. Although no public exploits have been reported yet, the vulnerability's characteristics make it highly exploitable once a proof-of-concept or exploit is developed. The affected devices are commonly deployed in enterprise and SMB telephony environments, making this a significant risk for organizations relying on these models for communication. The lack of available patches at the time of disclosure necessitates immediate mitigation steps to reduce exposure.

For European organizations, this vulnerability poses a significant threat to telephony infrastructure security. Successful exploitation can lead to complete device takeover, allowing attackers to intercept sensitive voice communications, alter call routing, or disrupt telephony services, impacting business operations and privacy compliance under regulations like GDPR. The root-level access gained can be leveraged to pivot into internal networks, potentially compromising other critical systems. Given the widespread use of Grandstream devices in European SMBs and enterprises, especially in sectors like finance, healthcare, and government, the risk of espionage, data leakage, and operational disruption is high. The vulnerability's unauthenticated nature increases the attack surface, particularly for devices exposed to untrusted networks or insufficiently segmented environments. The absence of known exploits currently provides a window for proactive defense, but the critical severity demands urgent attention to prevent future attacks.

1. Immediately restrict access to the HTTP API endpoint /cgi-bin/api.values.get by implementing network segmentation and firewall rules to block untrusted external access. 2. Disable or restrict HTTP management interfaces on Grandstream devices where possible, especially from WAN or public networks. 3. Monitor network traffic for unusual HTTP requests targeting the vulnerable endpoint and anomalous device behavior indicative of exploitation attempts. 4. Maintain an inventory of all affected Grandstream models in use and prioritize their isolation until patches are available. 5. Engage with Grandstream support channels to obtain security advisories and patches as soon as they are released. 6. Consider deploying intrusion detection/prevention systems (IDS/IPS) with signatures targeting exploitation attempts against this vulnerability. 7. Educate IT and security teams about the vulnerability to ensure rapid response to any suspicious activity. 8. Plan for device firmware updates and test patches in controlled environments before deployment to minimize operational disruption.