CVE-2026-3101: Intelbras TIP 635G Firmware RCE Vulnerability

CVE-2026-3101 Overview

A critical OS command injection vulnerability has been identified in the Intelbras TIP 635G VoIP phone running firmware version 1.12.3.5. This vulnerability exists within the Ping Handler component, where insufficient input validation allows attackers to inject arbitrary operating system commands. The vulnerability can be exploited remotely by authenticated users, potentially leading to complete device compromise with root-level access.

The exploit for this vulnerability has been made public, increasing the risk of widespread exploitation. Despite early disclosure attempts, the vendor (Intelbras) did not respond, leaving affected devices without an official patch.

Critical Impact

Remote authenticated attackers can achieve OS command injection leading to root-level remote code execution on affected Intelbras TIP 635G devices.

Affected Products

• Intelbras TIP 635G Firmware version 1.12.3.5
• Intelbras TIP 635G Hardware

Discovery Timeline

• 2026-02-24 - CVE-2026-3101 published to NVD
• 2026-02-26 - Last updated in NVD database

Technical Details for CVE-2026-3101

Vulnerability Analysis

This vulnerability is classified under CWE-77 (Improper Neutralization of Special Elements used in a Command) and CWE-78 (Improper Neutralization of Special Elements used in an OS Command). The Ping Handler component in the Intelbras TIP 635G firmware fails to properly sanitize user-supplied input before passing it to underlying system commands.

When an authenticated user interacts with the ping functionality, the input is directly incorporated into shell commands without adequate validation or escaping. This allows specially crafted input containing shell metacharacters or command separators to execute arbitrary commands on the underlying operating system with the privileges of the web application process, which in this case runs as root.

Root Cause

The root cause of this vulnerability lies in the Ping Handler's failure to implement proper input validation and sanitization. The component directly passes user-controlled data to system shell commands without escaping special characters such as ;, |, &, `, $(), and other shell metacharacters. This is a common anti-pattern in embedded device firmware where developer convenience takes precedence over security controls.

Attack Vector

The attack can be executed remotely over the network. An attacker with valid credentials to the device's web interface can exploit the Ping Handler functionality by injecting OS commands within the ping target parameter. Since the vulnerability requires authentication, attackers would first need to obtain valid credentials through default credentials, credential stuffing, or other means.

The exploitation typically involves submitting a malicious payload through the ping input field that includes command separators followed by arbitrary commands. Upon execution, these commands run in the context of the device's operating system, often with root privileges, enabling full device compromise.

For detailed technical analysis of the exploitation technique, refer to the Notion Analysis on Intelbras RCE.

Detection Methods for CVE-2026-3101

Indicators of Compromise

• Unusual outbound network connections from the Intelbras TIP 635G device to unknown external IP addresses
• Unexpected processes running on the device that are not part of normal VoIP phone operations
• Log entries showing malformed or suspicious ping requests containing shell metacharacters (;, |, &, backticks)
• Evidence of file system modifications or new files created in writable directories

Detection Strategies

• Monitor HTTP POST requests to the Ping Handler endpoint for payloads containing command injection patterns
• Implement network-based intrusion detection rules to identify command injection attempts targeting Intelbras devices
• Review device logs for authentication events followed by suspicious ping requests
• Deploy network segmentation to isolate IoT/VoIP devices and monitor cross-segment traffic

Monitoring Recommendations

• Enable verbose logging on network perimeter devices to capture traffic to and from Intelbras TIP 635G devices
• Implement SIEM correlation rules to detect patterns consistent with post-exploitation activity
• Conduct periodic firmware integrity verification if supported by the device

How to Mitigate CVE-2026-3101

Immediate Actions Required

• Restrict network access to the Intelbras TIP 635G web management interface to trusted administrative networks only
• Change default credentials and implement strong, unique passwords for all device accounts
• Place affected devices behind a firewall that blocks external access to the management interface
• Consider disabling the Ping Handler functionality if not required for operations

Patch Information

As of the last update on 2026-02-26, no official patch has been released by Intelbras. The vendor was contacted early about this disclosure but did not respond. Organizations should monitor Intelbras security advisories for future updates and consider device replacement if patches are not forthcoming.

For additional vulnerability details, see VulDB #347527.

Workarounds

• Implement network access control lists (ACLs) to restrict management interface access to specific trusted IP addresses
• Deploy the device behind a VPN to require authenticated network access before device interaction
• Use a web application firewall (WAF) to filter requests containing command injection patterns if management interface exposure is unavoidable
• Consider network isolation using VLANs to separate VoIP devices from critical infrastructure

# Example: Restrict management interface access via iptables on upstream firewall
iptables -A FORWARD -d <INTELBRAS_DEVICE_IP> -p tcp --dport 80 -s <TRUSTED_ADMIN_SUBNET> -j ACCEPT
iptables -A FORWARD -d <INTELBRAS_DEVICE_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <INTELBRAS_DEVICE_IP> -p tcp --dport 443 -s <TRUSTED_ADMIN_SUBNET> -j ACCEPT
iptables -A FORWARD -d <INTELBRAS_DEVICE_IP> -p tcp --dport 443 -j DROP