Source: cve@mitre.org
Alcatel ADSL modems allow remote attackers to access the Trivial File Transfer Protocol (TFTP) to modify firmware and configuration via a bounce attack from a system on the local area network (LAN) side, which is allowed to access TFTP without authentication.
Alcatel ADSL modems are vulnerable to a remote firmware modification attack. Attackers can leverage the unauthenticated TFTP service to upload malicious firmware, potentially leading to complete device compromise and network disruption. This vulnerability allows attackers to gain persistent access and control over the affected devices.
Step 1: Network Reconnaissance: The attacker identifies an Alcatel ADSL modem on the target network, likely by scanning for open ports or using network discovery tools.
Step 2: TFTP Access: The attacker, from a system on the LAN, connects to the modem's TFTP service, typically on UDP port 69. Authentication is not required.
Step 3: Firmware Preparation: The attacker crafts a malicious firmware image or configuration file designed to compromise the modem. This could include backdoors, credential stealers, or denial-of-service payloads.
Step 4: File Upload: The attacker uses the TFTP protocol to upload the malicious firmware or configuration file to the modem's storage.
Step 5: Firmware Update Trigger: The attacker may need to trigger a firmware update process, which could involve a specific command or a reboot. This step is dependent on the specific modem model and firmware.
Step 6: Device Compromise: The malicious firmware is installed, granting the attacker control over the modem and potentially the entire network.
The vulnerability stems from the Alcatel ADSL modems' insecure implementation of the TFTP service. The service allows unauthenticated access from the LAN side, enabling attackers to upload arbitrary files. The root cause is the lack of proper authentication and authorization checks before allowing TFTP operations, specifically file uploads. This design flaw allows attackers to overwrite the modem's firmware, configuration files, or other critical system files, leading to complete control of the device. The absence of input validation on the uploaded files could potentially lead to further vulnerabilities, such as buffer overflows or command injection, if the firmware update process is not secure.
While no specific APT groups are directly linked to this CVE, the ease of exploitation and potential for network-wide impact make it attractive to various threat actors. This vulnerability could be leveraged by attackers for initial access, persistence, or lateral movement. The vulnerability is not listed in the CISA KEV catalog, but the age and impact of the vulnerability make it a high priority for remediation.
Network traffic analysis: Monitor for unusual TFTP activity, especially file uploads from internal hosts to the modem on UDP port 69.
Log analysis: Review modem logs for suspicious TFTP requests, firmware update attempts, or unauthorized configuration changes.
File integrity monitoring: Implement file integrity monitoring on the modem's file system to detect unauthorized modifications to firmware or configuration files.
IDS/IPS signatures: Deploy intrusion detection/prevention systems with signatures that detect known exploit attempts against this vulnerability.
Honeypots: Deploy honeypots that mimic vulnerable Alcatel modems to attract and analyze attacker activity.
Replace vulnerable Alcatel ADSL modems with modern, secure devices that support up-to-date security protocols and firmware.
If replacement is not immediately feasible, isolate vulnerable modems on a separate network segment to limit the impact of a compromise.
Disable the TFTP service if it is not required for legitimate operations. If TFTP is necessary, restrict access to only authorized devices and implement strong authentication.
Regularly update the firmware of all network devices to the latest versions to patch known vulnerabilities.
Implement network segmentation to limit the blast radius of a potential compromise.
Monitor network traffic for suspicious activity, such as unauthorized file transfers or unusual network connections.
Conduct regular vulnerability scans to identify and address security weaknesses in the network infrastructure.