CVE-2018-25125 in DL4322D
Summary
by MITRE • 11/15/2025
Netis ADSL Router DL4322D firmware RTK 2.1.1 contains a buffer overflow vulnerability in the embedded FTP service that allows an authenticated remote user to trigger a denial of service. After logging in to the FTP service, sending an FTP command such as ABOR with an excessively long argument causes the service, and in practice the router, to crash or become unresponsive, resulting in a loss of availability for the device and connected users.
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Analysis
by VulDB Data Team • 11/16/2025
The CVE-2018-25125 vulnerability represents a critical buffer overflow flaw within the Netis ADSL Router DL4322D firmware version RTK 2.1.1, specifically affecting the embedded FTP service implementation. This vulnerability falls under the CWE-121 buffer overflow category, where insufficient bounds checking allows attackers to write beyond allocated memory boundaries. The flaw exists in the handling of FTP commands, particularly the ABOR command, which when supplied with an excessively long argument triggers memory corruption that leads to system instability.
The technical exploitation of this vulnerability requires an authenticated user to establish a connection to the router's FTP service, which typically operates on port 21. Once authenticated, the attacker can send maliciously crafted FTP commands with oversized parameters that exceed the buffer size allocated for command arguments. The embedded FTP service in this router firmware lacks proper input validation and boundary checking mechanisms, allowing the overflow to occur when the service attempts to process the ABOR command with arguments exceeding predetermined limits. This type of vulnerability aligns with ATT&CK technique T1210 - Exploitation of Remote Services, specifically targeting network infrastructure devices.
The operational impact of this vulnerability manifests as a complete denial of service condition for the affected router and all connected network users. When the buffer overflow occurs, the embedded FTP service crashes and subsequently causes the entire router to become unresponsive or reboot, creating a persistent availability issue that can disrupt network connectivity for extended periods. Network administrators may experience significant downtime as the device becomes inaccessible, requiring manual intervention to restore service. The vulnerability affects the core functionality of the router since the FTP service is integral to the device's management and operation capabilities, making it particularly dangerous for network infrastructure.
Mitigation strategies for CVE-2018-25125 should prioritize immediate firmware updates from the vendor or third-party security vendors, as this vulnerability affects the embedded software components that cannot be easily patched through conventional network security measures. Network administrators should implement strict access controls to limit FTP service exposure, disable unnecessary services, and monitor for suspicious FTP activity patterns that may indicate exploitation attempts. The vulnerability also highlights the importance of network segmentation and implementing network access control lists to prevent unauthorized access to router management interfaces. Organizations should consider deploying network monitoring tools that can detect unusual service behavior or crash patterns that may indicate exploitation of similar buffer overflow vulnerabilities, aligning with ATT&CK technique T1046 - Network Service Scanning to proactively identify and mitigate such threats.