This week, cybersecurity firm Rapid7 disclosed a critical vulnerability affecting Grandstream’s GXP1600 series phones, primarily used by small-to-medium businesses. This flaw, identified as CVE-2026-2329, poses a significant risk of call interception by unauthorized individuals.
Understanding the Vulnerability
The CVE-2026-2329 vulnerability is characterized as a stack-based buffer overflow, which allows remote code execution with root privileges on the device. This exploit can be carried out by an unauthenticated attacker, providing them with access to sensitive data stored on the devices.
Primarily impacting basic VoIP desktop phones, this vulnerability enables attackers to intercept calls by extracting critical information such as local and SIP account credentials. This information can then be used to redirect calls through infrastructure controlled by the attackers.
Potential Impact on Communications
Douglas McKee, Director of Vulnerability Intelligence at Rapid7, emphasized that attackers can manipulate the device’s SIP settings to reroute calls through a malicious proxy. Despite this redirection, users remain unaware, as the phones function normally—calls dial, displays light up, and dial tones are heard.
This silent interception allows for real-time relaying of sensitive conversations, including those about contracts, legal strategies, and personal matters. The risk is compounded by the fact that the exploitation of this flaw requires significant knowledge and skill, yet it lowers the barrier for potential attackers.
Mitigation and Response
The vulnerability was responsibly reported to Grandstream in January, and a firmware update (version 1.0.7.81) was quickly made available to address the issue. Users of affected devices are strongly encouraged to apply this update to mitigate the risk of exploitation.
Rapid7 has provided detailed technical information about the vulnerability, and Grandstream has released its own advisory. This proactive approach is crucial to protect against potential threats and ensure the security of communications.
Security professionals continue to monitor the situation, as Grandstream products have been targeted by threat actors in the past, including their use in botnet activities. The timely patching of vulnerabilities remains an essential practice for safeguarding sensitive communications and data.
