Technical Analysis of EUVD-2026-4968 (CVE-2026-1610): Hard-Coded Credentials in Tenda AX12 Pro V2

1. Vulnerability Assessment and Severity Evaluation

EUVD ID: EUVD-2026-4968 CVE ID: CVE-2026-1610 CVSS v4.0 Base Score: 9.2 (Critical) CVSS Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P

Severity Breakdown

• Attack Vector (AV:N): Network-based exploitation (remote attack possible).
• Attack Complexity (AC:H): High complexity due to required preconditions (e.g., knowledge of hard-coded credentials, network access).
• Attack Requirements (AT:N): No special conditions (e.g., user interaction) are needed.
• Privileges Required (PR:N): No authentication required.
• User Interaction (UI:N): No user interaction needed.
• Vulnerable Component (VC:H): High impact on confidentiality, integrity, and availability of the affected system.
• Subsequent System Impact (SC:N): No impact on downstream systems.
• Exploit Maturity (E:P): Proof-of-concept (PoC) exploit is publicly available.

Key Takeaways:

• The vulnerability allows unauthenticated remote attackers to gain access to the Telnet service using hard-coded credentials.
• Despite the high attack complexity, the publicly available exploit significantly increases the risk of exploitation.
• The critical severity (9.2) stems from the complete compromise potential (VC:H/VI:H/VA:H) of the affected device.

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2. Potential Attack Vectors and Exploitation Methods

Attack Surface

The vulnerability resides in the Telnet service of the Tenda AX12 Pro V2 router, which is exposed to:

• Local network (LAN) attacks (if Telnet is enabled internally).
• Remote attacks (if Telnet is exposed to the WAN, which is highly discouraged but possible due to misconfigurations).

Exploitation Steps

1. Reconnaissance:

   • Attacker scans for open Telnet ports (TCP/23) on the target device.
   • Identifies the Tenda AX12 Pro V2 via banner grabbing or fingerprinting.

2. Credential Discovery:

   • The attacker leverages hard-coded credentials (likely embedded in firmware or configuration files).
   • Publicly disclosed exploits (e.g., GitHub PoC) may reveal these credentials.

3. Initial Access:

   • Attacker logs in via Telnet using the hard-coded credentials.
   • Gains unrestricted shell access with root/administrative privileges.

4. Post-Exploitation:

   • Persistence: Installs backdoors, modifies firmware, or disables security features.
   • Lateral Movement: Uses the compromised router as a pivot point to attack other internal systems.
   • Data Exfiltration: Intercepts unencrypted traffic (e.g., HTTP, FTP) passing through the router.
   • Denial of Service (DoS): Disrupts network operations by modifying routing tables or crashing the device.

Exploitation Difficulty

• Known to be difficult (AC:H) due to:
  • Requirement for precise knowledge of the hard-coded credentials.
  • Potential rate-limiting or brute-force protections (though unlikely in consumer-grade routers).
  • Network segmentation may limit exposure (e.g., Telnet not exposed to WAN).
• However, public PoC availability lowers the barrier for script kiddies and automated attacks.

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3. Affected Systems and Software Versions

Vulnerable Product

• Vendor: Tenda
• Product: AX12 Pro V2 (Wi-Fi 6 Router)
• Affected Firmware Version: 16.03.49.24_cn (Chinese market variant)
• Component: Telnet Service (likely enabled by default or misconfigured)

Potential Impact Scope

• Consumer & SOHO Networks: Home users and small businesses using the affected router.
• Enterprise Edge Cases: If deployed in branch offices or remote locations without proper hardening.
• Geographic Focus: Primarily Chinese market (due to "_cn" firmware suffix), but similar vulnerabilities may exist in other regional variants.

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4. Recommended Mitigation Strategies

Immediate Actions (High Priority)

1. Disable Telnet Service:

   • Access the router’s admin panel (http://192.168.0.1 or similar) and disable Telnet if enabled.
   • Use SSH (if available) with strong credentials instead.

2. Apply Firmware Updates:

   • Check Tenda’s official website (Tenda Support) for patched firmware.
   • If no update is available, consider replacing the device if critical security is required.

3. Network-Level Protections:

   • Block Telnet (TCP/23) at the firewall (both inbound and outbound).
   • Segment the network to isolate the router from critical internal systems.
   • Monitor for unusual Telnet connections (e.g., via SIEM or IDS).

4. Change Default Credentials:

   • Even if Telnet is disabled, change all default admin credentials to prevent other attack vectors.

Long-Term Hardening

1. Disable Unnecessary Services:

   • Disable UPnP, WPS, and remote administration if not required.
   • Enable firewall rules to restrict access to the admin interface.

2. Implement Network Access Control (NAC):

   • Use MAC filtering or 802.1X authentication to limit device access.

3. Regular Vulnerability Scanning:

   • Use tools like OpenVAS, Nessus, or Nmap to detect exposed services.
   • Monitor CVE databases for new vulnerabilities in Tenda devices.

4. Replace End-of-Life (EOL) Devices:

   • If the router is no longer supported, migrate to a modern, actively maintained model.

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5. Impact on the European Cybersecurity Landscape

Regulatory & Compliance Implications

• NIS2 Directive (EU 2022/2555):
  • Organizations in critical sectors (e.g., energy, healthcare, transport) must ensure secure network infrastructure.
  • A compromised router could lead to supply chain attacks or lateral movement into critical systems.
• GDPR (EU 2016/679):
  • If the router is used in a business handling personal data, a breach could result in regulatory fines (up to 4% of global revenue).
• ENISA Guidelines:
  • The vulnerability aligns with ENISA’s "Threat Landscape for IoT" report, highlighting hard-coded credentials as a top risk in consumer-grade networking devices.

Threat to Critical Infrastructure

• SOHO & Remote Work Risks:
  • With the rise of remote work, compromised home routers can serve as entry points into corporate networks.
• Botnet Recruitment:
  • Attackers may enlist vulnerable routers into DDoS botnets (e.g., Mirai variants).
• Supply Chain Attacks:
  • If Tenda routers are used in ISP or enterprise deployments, a mass exploitation could lead to large-scale outages.

Geopolitical & Economic Factors

• Chinese Market Focus:
  • The "_cn" firmware suggests primary risk in China, but similar vulnerabilities may exist in European-market variants.
• Third-Party Exploit Availability:
  • The public PoC increases the risk of automated attacks by cybercriminals and APT groups.

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6. Technical Details for Security Professionals

Root Cause Analysis

• Hard-Coded Credentials:

  • The Telnet service in Tenda AX12 Pro V2 (16.03.49.24_cn) contains embedded credentials (likely in /etc/passwd, /etc/shadow, or a proprietary configuration file).
  • These credentials are not user-modifiable and may be identical across all devices of the same model/firmware.

• Firmware Analysis (Hypothetical):

  • A reverse engineering of the firmware (using Binwalk, Ghidra, or IDA Pro) would likely reveal:
    • Static credentials in plaintext or weakly obfuscated form.
    • Backdoor accounts with root privileges.
    • Lack of secure boot or firmware signing, allowing tampering.

Exploitation Proof-of-Concept (PoC)

• GitHub Reference: QIU-DIE/CVE/issues/49
• Expected Exploit Flow:

  # Step 1: Identify target (Nmap scan)
  nmap -p 23 --script telnet-brute <TARGET_IP>
  
  # Step 2: Connect via Telnet with hard-coded credentials
  telnet <TARGET_IP>
  # (Credentials likely disclosed in PoC)
  
  # Step 3: Gain root shell
  id  # Should return "uid=0(root)"
  

Detection & Forensics

• Indicators of Compromise (IoCs):

  • Unusual Telnet connections (e.g., from external IPs).
  • Modified /etc/passwd or /etc/shadow files.
  • Unexpected processes (e.g., nc, busybox, or custom malware).
  • Unauthorized firmware changes (e.g., md5sum mismatch).

• Log Analysis:

  • Check router logs for failed/successful Telnet login attempts.
  • Monitor outbound connections from the router (e.g., to C2 servers).

Reverse Engineering & Firmware Extraction

1. Download Firmware:
   • Obtain the latest firmware from Tenda’s website.
2. Extract Filesystem:

   binwalk -e AX12_Pro_V2_16.03.49.24_cn.bin
   

3. Analyze Binaries:
   • Use Ghidra or IDA Pro to inspect telnetd or related binaries.
   • Search for hard-coded strings (e.g., admin:password, root:toor).

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Conclusion & Recommendations

Summary of Risks

• Critical severity (9.2) due to unauthenticated remote access via hard-coded credentials.
• Public exploit availability increases the likelihood of automated attacks.
• High impact on confidentiality, integrity, and availability of the affected device.

Action Plan for Organizations

Priority	Action	Responsible Party
Critical	Disable Telnet immediately	Network Admins
Critical	Apply firmware updates (if available)	IT Security Team
High	Block Telnet at the firewall	SOC / Network Team
High	Monitor for IoCs (unusual Telnet logins)	Threat Hunters
Medium	Replace EOL/unpatched devices	Procurement / Management

Final Recommendations

• For Consumers: Disable Telnet and update firmware immediately.
• For Enterprises: Replace vulnerable routers if used in critical infrastructure.
• For Security Researchers: Analyze firmware for additional backdoors and report findings to Tenda.
• For Regulators: Enforce stricter IoT security standards (e.g., EU Cyber Resilience Act) to prevent hard-coded credentials in consumer devices.

References:

• VulDB Entry (EUVD-2026-4968)
• GitHub PoC (CVE-2026-1610)
• Tenda Official Support
• NIS2 Directive (EU 2022/2555)