CVE-2026-31196: ALTICE LABS GR140DG/IG RCE Vulnerability

CVE-2026-31196 Overview

CVE-2026-31196 is a command injection vulnerability in the traceroute diagnostic handler of /bin/httpd_clientside on Altice Labs and SFR France GR140DG and GR140IG fibre Customer Premises Equipment (CPE) gateways. The handler passes the user-supplied destAddr parameter into a system() call without sanitization. Authenticated attackers can inject shell command substitution sequences to execute arbitrary commands as root on the device. The flaw is tracked as an OS Command Injection weakness [CWE-78] and affects routers deployed widely across residential and small-business fibre subscriber networks.

Critical Impact

Authenticated remote attackers can achieve root-level code execution on the gateway, enabling full device takeover, traffic interception, and pivoting into the internal network.

Affected Products

• Altice Labs GR140DG fibre CPE/Router/Gateway
• Altice Labs GR140IG fibre CPE/Router/Gateway
• SFR France-branded GR140 series devices running /bin/httpd_clientside

Discovery Timeline

• 2026-05-05 - CVE-2026-31196 published to the National Vulnerability Database (NVD)
• 2026-05-07 - Last updated in NVD database

Technical Details for CVE-2026-31196

Vulnerability Analysis

The GR140DG and GR140IG gateways expose a web administration interface served by /bin/httpd_clientside. The interface includes a traceroute diagnostic feature that accepts a destination host through the destAddr HTTP parameter. The handler concatenates this parameter directly into a shell command string and passes it to system() for execution. Because the binary runs with root privileges, any injected command inherits full administrative rights on the underlying Linux operating system.

The vulnerability requires authentication, but credential reuse, default passwords on ISP-provisioned CPE, and exposed remote management interfaces commonly enable adversaries to clear that bar. The flaw is reachable over the network and yields complete confidentiality, integrity, and availability impact on the gateway.

Root Cause

The root cause is missing input validation and improper neutralization of special elements used in an OS command [CWE-78]. The traceroute handler trusts the destAddr field as a host argument and does not enforce a strict allowlist of IP addresses or hostnames. Shell metacharacters such as backticks, $(), ;, &&, and | pass through unchecked into the command line consumed by system().

Attack Vector

An authenticated attacker submits a crafted traceroute request with a destAddr value containing shell command substitution syntax. For example, a value such as 8.8.8.8;$(reboot) or 127.0.0.1`id` causes the embedded command to execute alongside the intended traceroute invocation. The injected payload runs as root, allowing the attacker to drop persistent backdoors, modify firmware, dump credentials from /etc, alter DNS settings, or use the gateway as a foothold for lateral movement onto subscriber LANs. Refer to the XEROD Security Advisory XEROD-2026-0002 for additional technical context.

Detection Methods for CVE-2026-31196

Indicators of Compromise

• HTTP requests to the device administration interface containing shell metacharacters (;, |, &, `, $() in the destAddr parameter.
• Unexpected outbound connections originating from the gateway to attacker-controlled infrastructure shortly after traceroute requests.
• New or modified files in writable firmware paths such as /tmp, /var, or /etc on the CPE.
• Configuration drift in DNS, DHCP, or firewall settings that subscribers did not initiate.

Detection Strategies

• Inspect web server and proxy logs for destAddr values that do not match a strict IPv4, IPv6, or hostname pattern.
• Apply intrusion detection signatures that flag command substitution syntax in HTTP POST bodies destined for CPE management endpoints.
• Correlate authentication events on the gateway with subsequent traceroute diagnostic invocations to surface anomalous administrative sessions.

Monitoring Recommendations

• Centralize syslog from CPE devices and alert on httpd_clientside process anomalies or unexpected child processes spawned from it.
• Monitor north-south traffic from gateway management IPs for command-and-control patterns and reverse shell beacons.
• Track failed and successful logins to the device web interface to detect credential stuffing preceding exploitation.

How to Mitigate CVE-2026-31196

Immediate Actions Required

• Disable remote WAN-side access to the gateway administration interface and restrict management to the LAN.
• Rotate administrative credentials on every GR140DG and GR140IG device, removing default or ISP-provisioned passwords.
• Contact Altice Labs or SFR France to confirm patch availability and request firmware updates for affected fleet devices.
• Segment subscriber networks so that a compromised gateway cannot pivot to sensitive internal assets.

Patch Information

No vendor patch URL is listed in the published advisory data at the time of writing. Operators should monitor Altice Labs and SFR France channels for firmware updates addressing the destAddr input handling in /bin/httpd_clientside. Refer to the XEROD Security Advisory XEROD-2026-0002 and the Altice Labs vendor site for further updates.

Workarounds

• Block external access to the device HTTP/HTTPS management ports at the upstream firewall or ISP edge.
• Deploy a web application firewall in front of bulk-managed CPE that strips shell metacharacters from diagnostic parameters.
• Disable the traceroute diagnostic feature in the web UI where the device configuration permits it.
• Limit administrative access to a dedicated management VLAN with strong access control lists.

# Example upstream ACL restricting CPE management access to a trusted jump host
iptables -A FORWARD -p tcp -d <CPE_IP> --dport 80  -s <ADMIN_HOST> -j ACCEPT
iptables -A FORWARD -p tcp -d <CPE_IP> --dport 443 -s <ADMIN_HOST> -j ACCEPT
iptables -A FORWARD -p tcp -d <CPE_IP> --dport 80  -j DROP
iptables -A FORWARD -p tcp -d <CPE_IP> --dport 443 -j DROP