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Introduction
A serious security vulnerability has been identified in ASUS RT-AX55 routers running firmware version 3.0.0.4.386.51598. This issue allows authenticated attackers to execute arbitrary OS commands, potentially compromising the device and gaining unauthorized access to sensitive systems or networks. With the CVSS score marked as 8.8 (High), the flaw has significant implications for home users and small businesses relying on this router model. Here’s a detailed breakdown of the vulnerability, its context, and what security experts — including Undercode — are saying about it.
CVE-2023-39780: A Deep Dive Into the Threat
The vulnerability CVE-2023-39780 is classified as an OS command injection flaw affecting ASUS RT-AX55 routers with firmware version 3.0.0.4.386.51598. Attackers who are already authenticated on the device can exploit a parameter named qos_bw_rulelist in the /start_apply.htm module to inject malicious commands directly into the operating system. This flaw doesn’t require user interaction, making it even more dangerous.
This vulnerability belongs to the Common Weakness Enumeration (CWE) category of OS Command Injection, which is notorious for allowing attackers to run shell commands on a host operating system. According to the CVSS v3.1 metrics, the attack vector is considered network-based, with low attack complexity, low privileges required, and no user interaction needed — all of which combine to give it a high impact rating on confidentiality, integrity, and availability.
Additionally, the vulnerability shares common traits with a group of similar flaws from the same environment:
CVE-2023-41345 (Token-Generated Module)
CVE-2023-41346 (Token-Refresh Module)
CVE-2023-41347 (Check Token Module)
CVE-2023-41348 (Code Authentication Module)
These vulnerabilities highlight a repeated pattern of poor input validation across different modules of the ASUS firmware ecosystem. The exposure increases risk significantly for users not keeping their devices up to date or unaware of these threats. Six public reference documents hosted on GitHub provide technical proof-of-concept (PoC) demonstrations for exploitation, reinforcing the severity and ease with which attackers could weaponize the issue.
What Undercode Say: 🔍 In-Depth Technical and Analytical Breakdown
Undercode’s analysis of CVE-2023-39780 reveals deeper concerns about firmware development practices in consumer-grade routers, particularly in how ASUS handles parameter validation in web modules:
- Weak Input Sanitization: The parameter
qos_bw_rulelistis insufficiently sanitized, meaning user-supplied data is directly passed into the operating system’s command line interface. This is a classic textbook mistake in web security. Exploitability Level: Since the vulnerability only requires an authenticated session, the real-world exploitability is moderate to high. Many users tend to keep default credentials or weak passwords, making brute-force or credential-stuffing attacks a feasible first step.
No User Interaction Required: The absence of a need for social engineering or phishing to trigger the exploit significantly increases its potential danger in automated or targeted attacks.
Unpatched Legacy Firmware: Devices not frequently updated by users (especially older hardware) are the most vulnerable. In scenarios where ASUS stops rolling out firmware updates, users could remain permanently exposed.
Linked Vulnerabilities: This isn’t an isolated flaw. The connection to other CVEs suggests systemic flaws in the firmware’s architecture — specifically in token and session management modules.
Network Threat Expansion: If exploited, attackers could pivot from the router to connected IoT devices or internal systems, creating a broader threat footprint within a local network.
Proof-of-Concept Availability: GitHub repositories with English-language documentation and sample exploit code lower the technical barrier for attackers worldwide. Script kiddies to advanced threat actors could weaponize it with minimal effort.
8. Security Posture Recommendations:
Immediate firmware upgrade (if patch available).
Disable remote web access to the router’s admin interface.
Enforce strong passwords and enable two-factor authentication where possible.
Use intrusion detection systems to log unusual outbound traffic.
- Vendor Accountability: Repeated issues across similar modules imply the need for ASUS to improve its Secure Software Development Lifecycle (SSDLC) practices. External audits should be considered for future firmware versions.
Wider Industry Implications: As router vulnerabilities become more prevalent, regulatory bodies may push for firmware transparency and mandatory security disclosures in consumer networking products.
🧐 Fact Checker Results
✅ CVSS 3.1 score confirms 8.8 High risk level.
✅ Six GitHub references provide valid and working PoC examples.
✅ ASUS has not released an official fix at the time of publishing.
🔮 Prediction
Given the exploitability and visibility of this vulnerability,
References:
Reported By: www.cve.org
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