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)
# 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
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
