CVE-2026-29126: IDC SFX2100 Privilege Escalation Flaw

CVE-2026-29126 is a privilege escalation vulnerability in IDC SFX2100 Satellite Receiver caused by world-writable file permissions. Attackers can exploit this to execute commands with root privileges. This article covers technical details, affected versions, impact assessment, and mitigation strategies.

CVE-2026-29126 Overview

CVE-2026-29126 is an incorrect permission assignment vulnerability affecting the International Data Casting (IDC) SFX2100 Satellite Receiver. The vulnerability exists in /etc/udhcpc/default.script, a BusyBox udhcpc DHCP event script that is configured as world-writable. This misconfiguration allows a local unprivileged attacker to modify the script and potentially execute arbitrary commands with root privileges, enabling local privilege escalation and persistence.

Critical Impact
Local unprivileged attackers can achieve root-level code execution by modifying a world-writable DHCP event script that executes automatically during DHCP lease events.

Affected Products

International Data Casting (IDC) SFX2100 Satellite Receiver
BusyBox udhcpc DHCP client component
Embedded Linux firmware with misconfigured /etc/udhcpc/default.script

Discovery Timeline

2026-03-05 - CVE-2026-29126 published to NVD
2026-03-05 - Last updated in NVD database

Technical Details for CVE-2026-29126

Vulnerability Analysis

This vulnerability stems from CWE-732 (Incorrect Permission Assignment for Critical Resource). The /etc/udhcpc/default.script file, which is executed by the BusyBox udhcpc DHCP client with root privileges, has been configured with world-writable permissions. This critical configuration error allows any local user, regardless of privilege level, to modify the script contents.

The udhcpc client invokes the default script during DHCP lifecycle events such as when a lease is obtained, renewed, or lost. Since the script runs as root, any malicious code injected by an attacker will execute with full system privileges. This creates a straightforward path from unprivileged local access to complete system compromise.

Root Cause

The root cause is improper file permission configuration on the DHCP event script. The /etc/udhcpc/default.script file should be owned by root and only writable by root (mode 755 or 744), but instead has been deployed with world-writable permissions (mode 777 or similar). This is a firmware-level misconfiguration in the IDC SFX2100 Satellite Receiver's embedded Linux system.

Attack Vector

The attack requires local access to the device. An attacker with any level of local access to the SFX2100 receiver can exploit this vulnerability by:

Writing malicious shell commands to /etc/udhcpc/default.script
Waiting for a DHCP event (lease obtain, renewal, or release) to trigger script execution
Alternatively, forcing a DHCP renewal to accelerate exploitation

The attacker could append reverse shell commands, create backdoor accounts, or install persistent rootkits. Once executed, the attacker gains root privileges and can maintain persistent access to the device.

For detailed technical analysis, refer to the Abdul MHS Blog Vulnerability Post.

Detection Methods for CVE-2026-29126

Indicators of Compromise

Modifications to /etc/udhcpc/default.script with unexpected content or timestamps
World-writable permissions on DHCP scripts (e.g., ls -la /etc/udhcpc/default.script showing write permissions for all users)
Unexpected network connections originating from the satellite receiver
Unauthorized user accounts or SSH keys added to the system

Detection Strategies

Monitor file integrity of /etc/udhcpc/default.script using checksums or file integrity monitoring tools
Audit file permissions across the embedded filesystem for world-writable files owned by root
Review system logs for unexpected DHCP client activity or script execution events
Implement network monitoring to detect anomalous outbound connections from satellite receiver devices

Monitoring Recommendations

Deploy endpoint detection and response (EDR) solutions capable of monitoring embedded Linux systems
Establish baseline configurations for satellite receivers and alert on deviations
Monitor for privilege escalation indicators such as unexpected root process spawning
Implement network segmentation to limit lateral movement from compromised satellite receivers

How to Mitigate CVE-2026-29126

Immediate Actions Required

Correct the file permissions on /etc/udhcpc/default.script to remove world-writable access (chmod 755 or 744)
Verify file ownership is set to root:root
Review the script contents for any unauthorized modifications and restore from a known-good backup if necessary
Audit all files in /etc/udhcpc/ and similar directories for permission misconfigurations

Patch Information

Contact International Data Casting (IDC) for firmware updates that address this permission misconfiguration. Monitor the vendor's security advisories and apply any available patches. Additional technical details are available at the Abdul MHS Blog Vulnerability Post.

Workarounds

Manually fix file permissions: chmod 755 /etc/udhcpc/default.script
Restrict physical and network access to the satellite receiver to trusted personnel only
Implement network segmentation to isolate satellite receivers from general network access
Consider using static IP configuration to disable DHCP and prevent script execution (if operationally feasible)

bash

# Configuration example - Fix file permissions
chmod 755 /etc/udhcpc/default.script
chown root:root /etc/udhcpc/default.script
ls -la /etc/udhcpc/default.script
# Expected output: -rwxr-xr-x 1 root root [size] [date] /etc/udhcpc/default.script