Comprehensive Technical Analysis of CVE-2025-69762

CVE ID: CVE-2025-69762 CVSS Score: 9.8 (Critical) Vulnerability Type: Stack-Based Buffer Overflow (Remote Code Execution) Affected Product: Tenda AX3 Router (Firmware v16.03.12.11) Vulnerable Component: formSetIptv (HTTP request handler) Exploitability: Remote, Unauthenticated

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1. Vulnerability Assessment & Severity Evaluation

Technical Overview

CVE-2025-69762 is a stack-based buffer overflow vulnerability in the Tenda AX3 router’s firmware, specifically in the formSetIptv function. The flaw arises due to improper bounds checking on the list parameter in an HTTP request, allowing an attacker to overwrite adjacent memory structures on the stack.

CVSS v3.1 Breakdown (Score: 9.8 - Critical)

Metric	Value	Justification
Attack Vector (AV)	Network (N)	Exploitable remotely over the network.
Attack Complexity (AC)	Low (L)	No special conditions required; trivial to exploit.
Privileges Required (PR)	None (N)	No authentication needed.
User Interaction (UI)	None (N)	Exploitable without user interaction.
Scope (S)	Unchanged (U)	Impact is confined to the vulnerable device.
Confidentiality (C)	High (H)	Remote code execution (RCE) enables full system compromise.
Integrity (I)	High (H)	Arbitrary code execution allows modification of system behavior.
Availability (A)	High (H)	Exploitation can crash the device or disrupt services.

Severity Justification

• Critical Impact: Successful exploitation leads to unauthenticated remote code execution (RCE) with root privileges, enabling full device takeover.
• Low Exploitation Barrier: The vulnerability is trivially exploitable via crafted HTTP requests, requiring no prior access or user interaction.
• Widespread Exposure: Tenda routers are commonly deployed in home and small business networks, increasing the attack surface.

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2. Potential Attack Vectors & Exploitation Methods

Exploitation Mechanism

1. Vulnerable Endpoint:

   • The formSetIptv function processes HTTP requests (likely via the router’s web interface or API).
   • The list parameter is improperly sanitized, allowing an attacker to inject an oversized input that overflows the stack buffer.

2. Stack Overflow Exploitation:

   • The attacker sends a maliciously crafted HTTP request with an excessively long list parameter.
   • The input overwrites the return address on the stack, redirecting execution to attacker-controlled memory (e.g., shellcode or ROP chain).
   • If ASLR/DEP are not properly enforced, the attacker can achieve arbitrary code execution.

3. Post-Exploitation Impact:

   • Device Takeover: Execution of arbitrary commands with root privileges.
   • Network Pivoting: Use of the compromised router as a foothold for lateral movement.
   • Botnet Recruitment: Enlistment into a DDoS botnet (e.g., Mirai variants).
   • Data Exfiltration: Interception of unencrypted traffic or theft of stored credentials.

Proof-of-Concept (PoC) Exploitation Steps

1. Identify Target:

   • Scan for Tenda AX3 routers (e.g., via Shodan, Censys, or masscan).
   • Verify firmware version (16.03.12.11).

2. Craft Exploit Payload:

   • Send an HTTP POST request to /goform/formSetIptv with a malicious list parameter:

     POST /goform/formSetIptv HTTP/1.1
     Host: <TARGET_IP>
     Content-Type: application/x-www-form-urlencoded
     Content-Length: <LENGTH>
     
     list=<OVERFLOW_PAYLOAD>&other_params=...
     

   • The OVERFLOW_PAYLOAD should:
     • Fill the buffer (e.g., 1024+ bytes).
     • Overwrite the saved return address with a ROP gadget or shellcode address.
     • Include NOP sleds and shellcode (e.g., reverse shell, bind shell).

3. Bypass Mitigations (if present):

   • ASLR Bypass: Leak memory addresses via information disclosure (e.g., via printf or other functions).
   • DEP Bypass: Use Return-Oriented Programming (ROP) to execute code in executable memory regions.
   • Stack Canaries: If present, brute-force or leak the canary value.

4. Achieve RCE:

   • If successful, the attacker gains a root shell on the device.

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3. Affected Systems & Software Versions

Vulnerable Product

• Device: Tenda AX3 Wi-Fi 6 Router
• Firmware Version: v16.03.12.11 (confirmed vulnerable)
• Likely Affected Versions:
  • Earlier versions of the AX3 firmware may also be vulnerable if they share the same codebase.
  • Other Tenda router models using similar firmware may be affected (requires further analysis).

Detection Methods

• Firmware Analysis:

  • Extract firmware (e.g., via binwalk, Firmware Mod Kit) and analyze the formSetIptv function in httpd or similar binaries.
  • Look for unsafe functions (strcpy, sprintf, gets) or lack of bounds checking.

• Network Scanning:

  • Use Nmap to fingerprint Tenda AX3 routers:

    nmap -p 80,443 --script http-title <TARGET_IP> | grep "Tenda"
    

  • Check for the firmware version via the web interface or HTTP headers.

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4. Recommended Mitigation Strategies

Immediate Actions

1. Apply Vendor Patch:

   • Check for firmware updates from Tenda’s official website.
   • If no patch is available, disable the vulnerable service (e.g., IPTV configuration) if not in use.

2. Network-Level Protections:

   • Restrict Access: Block external access to the router’s web interface (port 80/443) via firewall rules.
   • Segmentation: Isolate the router in a DMZ or separate VLAN to limit lateral movement.
   • Intrusion Prevention: Deploy an IPS/IDS (e.g., Snort, Suricata) to detect and block exploit attempts:

     alert tcp any any -> $HOME_NET 80 (msg:"Tenda AX3 formSetIptv Buffer Overflow Attempt"; flow:to_server,established; content:"POST /goform/formSetIptv"; nocase; content:"list="; nocase; pcre:"/list=.{1024,}/"; sid:1000001; rev:1;)
     

3. Temporary Workarounds:

   • Disable IPTV Configuration: If the formSetIptv endpoint is not required, disable it via the router’s admin panel.
   • Rate Limiting: Implement rate limiting on the web interface to slow down brute-force attacks.

Long-Term Remediation

1. Firmware Hardening:

   • Input Validation: Ensure all user-supplied inputs are length-checked before processing.
   • Safe Functions: Replace unsafe functions (strcpy, sprintf) with bounded alternatives (strncpy, snprintf).
   • Stack Protections: Enable stack canaries, ASLR, and NX/DEP in the firmware build.

2. Vendor Coordination:

   • Responsible Disclosure: Report the vulnerability to Tenda (if not already done) to expedite patching.
   • CVE Monitoring: Track updates from CISA, MITRE, and Tenda’s security advisories.

3. User Awareness:

   • Educate users on the risks of default credentials and unpatched firmware.
   • Encourage regular firmware updates and network monitoring.

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5. Impact on the Cybersecurity Landscape

Broader Implications

1. IoT & Router Security Crisis:

   • This vulnerability is part of a growing trend of critical flaws in consumer-grade routers, which are often poorly secured and rarely updated.
   • Similar vulnerabilities (e.g., CVE-2021-41773 in Tenda AC15, CVE-2020-10987 in Tenda AC10) highlight systemic issues in IoT security.

2. Botnet & Malware Threats:

   • Exploitable routers are prime targets for botnet operators (e.g., Mirai, Mozi, Gafgyt).
   • A wormable exploit could lead to large-scale infections, as seen with VPNFilter and Mirai.

3. Supply Chain Risks:

   • Many SOHO routers (including Tenda) are OEM devices rebranded by ISPs, increasing the supply chain attack surface.
   • A single vulnerability can affect millions of devices globally.

4. Regulatory & Compliance Impact:

   • GDPR, CCPA, and other regulations may impose fines on vendors for negligent security practices.
   • CISA’s Binding Operational Directive (BOD) 22-01 may require federal agencies to mitigate this vulnerability if it affects critical infrastructure.

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6. Technical Details for Security Professionals

Root Cause Analysis

• Vulnerable Function: formSetIptv in the router’s HTTP daemon (httpd).
• Flaw: The list parameter is copied into a fixed-size stack buffer without length validation.
• Code Snippet (Hypothetical):

  void formSetIptv() {
      char list[256];  // Fixed-size stack buffer
      char *user_input = get_http_param("list");  // Untrusted input
      strcpy(list, user_input);  // UNSAFE: No bounds checking
      // ... further processing
  }
  

• Exploitation Primitive:
  • Stack Smashing: Overwrite the return address to redirect execution.
  • ROP Chain: If DEP is enabled, construct a Return-Oriented Programming (ROP) chain to bypass NX.

Exploit Development Considerations

1. Memory Layout Analysis:

   • Use GDB (with QEMU emulation) to debug the firmware.
   • Identify stack layout, libc addresses, and ROP gadgets (e.g., using ROPgadget).

2. Bypass Techniques:

   • ASLR Bypass: Leak memory addresses via format string vulnerabilities or information disclosure.
   • Stack Canary Bypass: Brute-force or leak the canary value.
   • DEP Bypass: Use mprotect() ROP gadgets to mark memory as executable.

3. Shellcode Considerations:

   • MIPS/ARM Architecture: Tenda routers typically run on MIPS or ARM (e.g., mipsel).
   • Shellcode Example (MIPS Reverse Shell):

     # MIPS reverse shell shellcode (adjust IP/PORT)
     shellcode = (
         "\x24\x0f\xff\xfa"  # li $t7, -6
         "\x01\xe0\x78\x27"  # nor $t7, $t7, $zero
         "\x21\xe4\xff\xfd"  # addi $a0, $t7, -3
         "\x21\xe5\xff\xfd"  # addi $a1, $t7, -3
         "\x28\x06\xff\xff"  # slti $a2, $zero, -1
         "\x24\x02\x10\x57"  # li $v0, 4183 (sys_socket)
         "\x01\x01\x01\x0c"  # syscall 0x40404
         "\xaf\xa2\xff\xff"  # sw $v0, -1($sp)
         "\x8f\xa4\xff\xff"  # lw $a0, -1($sp)
         "\x24\x0f\xff\xfd"  # li $t7, -3
         "\x01\xe0\x78\x27"  # nor $t7, $t7, $zero
         "\x8f\xa5\xff\xff"  # lw $a1, -1($sp)
         "\x24\x0c\xff\xef"  # li $t4, -17
         "\x01\x80\x30\x27"  # nor $a2, $t4, $zero
         "\x24\x02\x10\x4a"  # li $v0, 4170 (sys_connect)
         "\x01\x01\x01\x0c"  # syscall 0x40404
         # ... (additional shellcode for execve)
     )
     

4. Post-Exploitation:

   • Persistence: Modify /etc/init.d/rc.local to execute a backdoor on boot.
   • Lateral Movement: Scan the internal network for other vulnerable devices.
   • Data Exfiltration: Use curl, wget, or nc to exfiltrate sensitive data.

Detection & Forensics

1. Network Signatures:

   • Snort/Suricata Rule:

     alert tcp any any -> $HOME_NET 80 (msg:"Tenda AX3 formSetIptv Buffer Overflow Attempt"; flow:to_server,established; content:"POST /goform/formSetIptv"; nocase; content:"list="; nocase; pcre:"/list=.{1024,}/"; sid:1000001; rev:1;)
     

   • Zeek/Bro Logs: Monitor for unusually large HTTP POST requests to /goform/formSetIptv.

2. Endpoint Detection:

   • Firmware Integrity Checks: Use Tripwire or AIDE to detect unauthorized modifications.
   • Process Monitoring: Look for unexpected child processes of httpd.

3. Forensic Artifacts:

   • Logs: Check /var/log/httpd.log for malformed requests.
   • Memory Analysis: Use Volatility (if memory dumps are available) to detect shellcode execution.
   • File System Analysis: Look for unauthorized modifications in /etc/passwd, /etc/shadow, or /etc/init.d/.

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Conclusion & Recommendations

CVE-2025-69762 represents a critical remote code execution vulnerability in Tenda AX3 routers, posing significant risks to home and small business networks. Given the low exploitation barrier and high impact, immediate action is required:

1. Patch Management: Apply vendor updates as soon as they become available.
2. Network Hardening: Restrict access to the router’s web interface and deploy IPS/IDS.
3. Monitoring: Implement continuous monitoring for exploit attempts.
4. Vendor Engagement: Encourage Tenda to improve firmware security and release patches promptly.

Security teams should prioritize this vulnerability due to its wormable potential and broad attack surface. Organizations using Tenda AX3 routers should assume compromise and conduct forensic analysis if exploitation is suspected.

For further research, security professionals are encouraged to:

• Reverse-engineer the firmware to identify additional vulnerabilities.
• Develop detection rules for SIEM/EDR solutions.
• Contribute to open-source IoT security projects (e.g., Firmware Analysis Toolkit, Binwalk).

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References:

• MITRE CVE Entry
• [Tenda Security Advisory (if available)]
• [Exploit-DB / Metasploit Modules (when published)]