Critical Grandstream Phone System Vulnerability Exposes Calls to Eavesdropping and Interception Attacks
Critical Vulnerability in Grandstream’s GXP1600 Series VoIP Phones
A critical vulnerability in Grandstream’s GXP1600 series VoIP phones has been discovered, allowing threat actors to intercept calls. The vulnerability, tracked as CVE-2026-2329, is a stack-based buffer overflow that can be exploited by an unauthenticated attacker to remotely execute code with root privileges on the targeted device.
Vulnerability Impact
The GXP1600 series is primarily used by small-to-medium businesses, and the vulnerability could be exploited to extract sensitive information, including local and SIP account credentials, from vulnerable phones. This would enable an attacker to intercept and eavesdrop on calls, potentially accessing sensitive information such as contract negotiations, legal strategies, and personal matters.
“With root access, an attacker can reconfigure the device’s SIP settings to point to infrastructure they control, effectively creating a malicious SIP proxy. This would allow the attacker to intercept calls without the user’s knowledge, as the device would still appear to be functioning normally.” – Douglas McKee, director of vulnerability intelligence at Rapid7
However, McKee noted that exploitation of the vulnerability requires a certain level of knowledge and skill, stating that “this isn’t a one-click exploit with fireworks and a victory banner.” Nevertheless, the vulnerability does lower the barrier for potential attackers, making it a concern for organizations operating these devices in exposed or lightly-segmented environments.
Fix and Recommendations
Grandstream has released a patched firmware version (1.0.7.81) to address the vulnerability, which was responsibly disclosed to the company in January. Rapid7 has also released technical details for CVE-2026-2329, and Grandstream has published its own advisory for the vulnerability.
It’s worth noting that Grandstream products have been targeted by threat actors in the past, including being ensnared in botnets. Organizations using the GXP1600 series phones should prioritize updating to the patched firmware version to prevent potential exploitation of this vulnerability.
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