CVE-2026-28778: IDC SFX SuperFlex Receiver RCE Vulnerability

CVE-2026-28778 Overview

International Datacasting Corporation (IDC) SFX Series SuperFlex Satellite Receiver contains undocumented, hardcoded credentials for the xd user account. This vulnerability allows a remote unauthenticated attacker to log in via FTP using these insecure credentials. Because the xd user has write permissions to their home directory where root-executed binaries and symlinks (such as those invoked by xdstartstop) are stored, the attacker can overwrite these files or manipulate symlinks to achieve arbitrary code execution as the root user.

Critical Impact

Remote unauthenticated attackers can gain root-level code execution on vulnerable satellite receiver devices by exploiting hardcoded FTP credentials and leveraging privileged file overwrites.

Affected Products

• International Datacasting Corporation (IDC) SFX Series SuperFlex Satellite Receiver

Discovery Timeline

• 2026-03-04 - CVE CVE-2026-28778 published to NVD
• 2026-03-05 - Last updated in NVD database

Technical Details for CVE-2026-28778

Vulnerability Analysis

This vulnerability represents a classic hardcoded credentials flaw (CWE-798) combined with improper privilege management that creates a complete attack chain from unauthenticated network access to root-level compromise. The IDC SFX Series SuperFlex Satellite Receiver ships with an undocumented xd user account containing weak or default credentials that are accessible over FTP.

The critical escalation path occurs because the xd user's home directory contains binaries and symbolic links that are executed with root privileges. Specifically, scripts or processes like xdstartstop run as root but operate on files within the xd user's writable directory. This architectural flaw allows an attacker with xd account access to replace legitimate executables or manipulate symlinks to point to attacker-controlled payloads.

Root Cause

The root cause of this vulnerability is twofold:

1. Hardcoded Credentials (CWE-798): The firmware contains undocumented, hardcoded credentials for the xd user account that cannot be changed by administrators and are identical across all devices.

2. Improper Privilege Separation: Root-executed processes rely on files stored in a user-writable directory, violating the principle of least privilege. The xdstartstop service and related binaries execute with elevated privileges but trust content from the xd user's home directory.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability through the following steps:

1. The attacker identifies an exposed FTP service on the target satellite receiver
2. Using the hardcoded xd credentials, the attacker authenticates to the FTP service
3. Once logged in, the attacker navigates to the xd user's home directory
4. The attacker identifies root-executed binaries or symbolic links within this directory
5. The attacker overwrites a binary with a malicious payload or manipulates symlinks to point to attacker-controlled files
6. When the system executes xdstartstop or similar privileged processes, the attacker's payload runs with root privileges

The attack can be executed remotely without any prior access to the device. The hardcoded credentials effectively bypass all authentication controls, and the privilege escalation occurs automatically when the system performs routine operations.

Detection Methods for CVE-2026-28778

Indicators of Compromise

• Unexpected FTP login attempts or successful authentications to satellite receiver devices, particularly using the xd username
• Modified file timestamps or checksums for binaries in the xd user's home directory
• New or altered symbolic links in /home/xd/ or related directories pointing to unexpected locations
• Unusual process execution chains where xdstartstop or related services spawn unexpected child processes

Detection Strategies

• Monitor FTP authentication logs for successful logins using the xd account, especially from external or unexpected IP addresses
• Implement file integrity monitoring (FIM) on critical binaries and directories within the xd user's home directory
• Deploy network intrusion detection rules to alert on FTP traffic to satellite receiver management interfaces from untrusted networks
• Regularly audit symbolic links in privileged execution paths for unexpected modifications

Monitoring Recommendations

• Segment satellite receiver devices on isolated network segments with strict firewall rules blocking external FTP access
• Configure SIEM alerts for any FTP authentication events to IDC satellite receiver devices
• Establish baseline file hashes for binaries in the xd home directory and alert on deviations
• Monitor for privilege escalation indicators such as unexpected root process spawning from user-owned directories

How to Mitigate CVE-2026-28778

Immediate Actions Required

• Block FTP access (port 21) to all IDC SFX Series SuperFlex Satellite Receivers from untrusted networks immediately
• Implement network segmentation to isolate satellite receiver infrastructure from general network access
• Audit existing devices for signs of compromise by checking file integrity in the xd user's home directory
• Contact International Datacasting Corporation for firmware updates or official remediation guidance

Patch Information

No official patch information is currently available from International Datacasting Corporation. Organizations should consult the Abdul MHS Blog Vulnerabilities Post for additional technical details and monitor vendor communications for security updates.

Workarounds

• Disable FTP services on affected devices if not required for operations
• Implement strict network access controls limiting connectivity to satellite receivers to authorized management stations only
• Deploy host-based or network-based firewalls to block FTP access from all but explicitly authorized IP addresses
• Consider implementing additional authentication layers such as VPN requirements before accessing device management interfaces

# Example firewall rule to block FTP access to satellite receivers
# Replace 192.168.1.100 with the actual IP of your IDC SFX device
iptables -A INPUT -p tcp --dport 21 -d 192.168.1.100 -j DROP

# Allow only specific management station (replace with your management IP)
iptables -I INPUT -p tcp --dport 21 -s 10.0.0.50 -d 192.168.1.100 -j ACCEPT