Critical Vulnerability in Grandstream GXP1600 VoIP Phones: CVE-2026-2329
Executive Summary
In February 2026, a critical vulnerability (CVE-2026-2329) was discovered in Grandstream's GXP1600 series VoIP phones, affecting models GXP1610, GXP1615, GXP1620, GXP1625, GXP1628, and GXP1630. This unauthenticated stack-based buffer overflow in the HTTP API endpoint "/cgi-bin/api.values.get" allows remote attackers to execute arbitrary code with root privileges. Exploitation could lead to unauthorized access, interception of VoIP communications, and potential eavesdropping on sensitive conversations. (rapid7.com)
The incident underscores the importance of promptly applying security patches and monitoring VoIP infrastructure for vulnerabilities. Organizations using these devices should update to firmware version 1.0.7.81 to mitigate the risk. (rapid7.com)
Why This Matters Now
The CVE-2026-2329 vulnerability in Grandstream's GXP1600 series VoIP phones allows unauthenticated remote code execution, posing significant risks of unauthorized access and eavesdropping. Immediate firmware updates are essential to secure communications and prevent potential breaches.
Attack Path Analysis
An attacker exploited an unauthenticated buffer overflow vulnerability in Grandstream GXP1600 series VoIP phones to gain root access. They escalated privileges to root, enabling full control over the device. The attacker then moved laterally within the network, targeting other devices. They established a command and control channel to maintain persistent access. Sensitive data was exfiltrated from the compromised devices. Finally, the attacker reconfigured the devices to use a malicious SIP proxy, intercepting and eavesdropping on VoIP communications.
Kill Chain Progression
Initial Compromise
Description
An attacker exploited an unauthenticated stack-based buffer overflow vulnerability in the HTTP API endpoint of Grandstream GXP1600 series VoIP phones, allowing remote code execution with root privileges.
Related CVEs
CVE-2026-2329
CVSS 9.3An unauthenticated stack-based buffer overflow in the web-based API service of Grandstream GXP1600 series VoIP phones allows remote attackers to execute arbitrary code with root privileges.
Affected Products:
Grandstream GXP1610 – < 1.0.7.81
Grandstream GXP1615 – < 1.0.7.81
Grandstream GXP1620 – < 1.0.7.81
Grandstream GXP1625 – < 1.0.7.81
Grandstream GXP1628 – < 1.0.7.81
Grandstream GXP1630 – < 1.0.7.81
Exploit Status:
proof of concept
MITRE ATT&CK® Techniques
Exploit Public-Facing Application
Exploitation for Client Execution
Exploitation for Privilege Escalation
Valid Accounts
Application or System Exploitation
Potential Compliance Exposure
Mapping incident impact across multiple compliance frameworks.
PCI DSS 4.0 – Ensure that all system components and software are protected from known vulnerabilities by installing applicable vendor-supplied security patches.
Control ID: 6.2
NYDFS 23 NYCRR 500 – Cybersecurity Policy
Control ID: 500.03
DORA – ICT Risk Management Framework
Control ID: Article 5
CISA ZTMM 2.0 – Identity
Control ID: Pillar 1
NIS2 Directive – Cybersecurity Risk Management Measures
Control ID: Article 21
Sector Implications
Industry-specific impact of the vulnerabilities, including operational, regulatory, and cloud security risks.
Telecommunications
Critical exposure as primary VoIP infrastructure provider. Remote code execution vulnerability enables call interception, credential theft, and network compromise across telecommunications networks.
Financial Services
High-value target for attackers seeking to intercept financial communications, compromise voice banking systems, and exploit trusted communication channels for fraud operations.
Health Care / Life Sciences
HIPAA compliance violations through intercepted patient communications. Stack-based buffer overflow enables attackers to access sensitive medical discussions and compromise telehealth systems.
Government Administration
National security implications from compromised government VoIP systems. Unauthenticated remote code execution allows foreign adversaries to eavesdrop on sensitive official communications.
Sources
- Grandstream GXP1600 VoIP Phones Exposed to Unauthenticated Remote Code Executionhttps://thehackernews.com/2026/02/grandstream-gxp1600-voip-phones-exposed.htmlVerified
- CVE-2026-2329: Critical Unauthenticated Stack Buffer Overflow in Grandstream GXP1600 VoIP Phones (FIXED)https://www.rapid7.com/blog/post/ve-cve-2026-2329-critical-unauthenticated-stack-buffer-overflow-in-grandstream-gxp1600-voip-phones-fixed/Verified
- Add exploit (CVE-2026-2329) and auxiliary modules for the Grandstream GXP1600 serieshttps://github.com/rapid7/metasploit-framework/pull/20983Verified
- Firmware - Grandstream Networkshttps://www.grandstream.com/support/firmwareVerified
Frequently Asked Questions
Cloud Native Security Fabric Mitigations and ControlsCNSF
Aviatrix Zero Trust CNSF is pertinent to this incident as it could likely limit the attacker's ability to move laterally, establish command channels, and exfiltrate data by enforcing strict segmentation and controlled egress policies.
Control: Cloud Native Security Fabric (CNSF)
Mitigation: The attacker's initial access to the VoIP phone may have been constrained, potentially reducing the scope of the compromise.
Control: Zero Trust Segmentation
Mitigation: The attacker's ability to escalate privileges may have been limited, potentially reducing the impact of the compromise.
Control: East-West Traffic Security
Mitigation: The attacker's lateral movement within the network could have been constrained, likely reducing the spread of the attack.
Control: Multicloud Visibility & Control
Mitigation: The attacker's ability to establish command and control channels may have been limited, potentially reducing persistent access.
Control: Egress Security & Policy Enforcement
Mitigation: The attacker's data exfiltration efforts could have been constrained, likely reducing data loss.
The attacker's ability to reconfigure devices for malicious purposes may have been limited, potentially reducing the impact on VoIP communications.
Impact at a Glance
Affected Business Functions
- VoIP Communication
- Internal Communications
Estimated downtime: 3 days
Estimated loss: $50,000
Potential exposure of VoIP call data and user credentials.
Recommended Actions
Key Takeaways & Next Steps
- • Apply the latest firmware updates (version 1.0.7.81) to all Grandstream GXP1600 series VoIP phones to remediate CVE-2026-2329.
- • Implement Zero Trust Segmentation to restrict device-to-device communication, limiting lateral movement opportunities.
- • Deploy East-West Traffic Security controls to monitor and control internal network traffic, detecting unauthorized movements.
- • Utilize Multicloud Visibility & Control solutions to gain comprehensive insights into network activities and enforce centralized policies.
- • Establish Egress Security & Policy Enforcement mechanisms to control outbound traffic, preventing unauthorized data exfiltration.
