CVE-2025-67112: Sercomm SCE4255W Privilege Escalation

CVE-2025-67112 Overview

CVE-2025-67112 is a cryptographic vulnerability affecting the Sercomm SCE4255W (FreedomFi Englewood) small cell device. The firmware contains a hard-coded AES-256-CBC encryption key within the configuration backup and restore implementation. Remote authenticated users can exploit this weakness to decrypt device configuration backups, modify sensitive settings including credentials, re-encrypt the configuration, and import it back into the device via the GUI import/export functions—resulting in credential manipulation and privilege escalation.

Critical Impact

Authenticated attackers can fully compromise device configurations by exploiting the hard-coded encryption key, enabling credential theft, unauthorized privilege escalation, and complete device takeover.

Affected Products

• Sercomm SCE4255W (FreedomFi Englewood) firmware versions before DG3934v3@2308041842

Discovery Timeline

• 2026-03-19 - CVE CVE-2025-67112 published to NVD
• 2026-03-19 - Last updated in NVD database

Technical Details for CVE-2025-67112

Vulnerability Analysis

This vulnerability stems from a fundamental cryptographic implementation flaw in the Sercomm SCE4255W firmware. The device uses AES-256-CBC encryption to protect configuration backup files that can be exported and imported through the web-based GUI. However, the encryption key used to protect these configuration files is hard-coded directly into the firmware, making it extractable through firmware analysis.

Once an attacker obtains the hard-coded key, they can decrypt any configuration backup exported from the device. The decrypted configuration contains sensitive information including administrative credentials, network settings, and device parameters. An attacker can modify these values—such as changing administrator passwords or elevating user privileges—then re-encrypt the configuration using the same hard-coded key and import it back into the device through the standard GUI interface.

This attack requires authenticated access to the device's web interface to export and import configuration files, but the authentication level required may be minimal depending on the device's access control configuration.

Root Cause

The root cause of this vulnerability is the use of hard-coded cryptographic material (CWE-321: Use of Hard-coded Cryptographic Key). The firmware developers embedded a static AES-256-CBC key directly in the firmware binary rather than implementing proper key derivation mechanisms or unique per-device keys. This design flaw means all devices running vulnerable firmware versions share the same encryption key, and once extracted, the key can be used to compromise any affected device.

Attack Vector

The attack vector requires an authenticated user with access to the device's web-based management GUI. The exploitation flow involves:

1. Exporting a configuration backup through the GUI export function
2. Extracting the hard-coded AES-256-CBC key from the firmware (one-time effort applicable to all devices)
3. Decrypting the configuration backup using the extracted key
4. Modifying sensitive parameters such as credentials or privilege levels
5. Re-encrypting the modified configuration with the same key
6. Importing the malicious configuration through the GUI import function

The vulnerability mechanism relies on the predictable nature of the hard-coded key. Because all devices running the vulnerable firmware use the same static key, an attacker who has analyzed the firmware once can decrypt and manipulate configurations from any device running that firmware version. Technical details regarding the specific key extraction methodology can be found in the Nero Team blog post.

Detection Methods for CVE-2025-67112

Indicators of Compromise

• Unexpected configuration changes on the device, particularly to administrative credentials or user privilege levels
• Configuration import events in device logs from unexpected sources or at unusual times
• Multiple configuration export operations followed by import operations within a short timeframe
• Unauthorized administrative accounts appearing on the device

Detection Strategies

• Monitor device audit logs for configuration import/export activities and correlate with authorized change windows
• Implement network monitoring to detect unusual traffic to the device management interface
• Establish baseline configurations and perform periodic integrity checks to identify unauthorized modifications
• Review user account listings on devices for unauthorized privilege escalations or new administrative accounts

Monitoring Recommendations

• Enable verbose logging on device management interfaces and forward logs to a centralized SIEM
• Configure alerts for any configuration changes outside of scheduled maintenance windows
• Implement network segmentation to restrict access to device management interfaces
• Monitor for firmware analysis activities on your network that could indicate attackers preparing to extract the hard-coded key

How to Mitigate CVE-2025-67112

Immediate Actions Required

• Update affected Sercomm SCE4255W devices to firmware version DG3934v3@2308041842 or later
• Restrict network access to the device management GUI to trusted administrative networks only
• Review and rotate all credentials stored on affected devices after patching
• Audit configuration history for any unauthorized changes that may have been made prior to patching

Patch Information

The vulnerability is addressed in firmware version DG3934v3@2308041842 and later. Organizations should obtain the updated firmware from FreedomFi or through their authorized distribution channels. Additional device information can be found in the FCC Report Document.

Workarounds

• Implement strict network access controls to limit which systems can access the device management interface
• Disable or restrict configuration export/import functionality if not operationally required
• Deploy network monitoring to detect and alert on configuration file transfers to/from the device
• Consider isolating affected devices on a dedicated management VLAN with enhanced monitoring until patching is complete

# Network segmentation example - restrict management access
# Example iptables rules to limit access to device management interface
iptables -A INPUT -p tcp --dport 443 -s 10.0.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
iptables -A INPUT -p tcp --dport 80 -s 10.0.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP