CVE-2025-56007

Executive Summary

CVE-2025-56007 is a critical CRLF injection vulnerability in KeeneticOS, affecting versions prior to 4.3. The flaw resides in the /auth API endpoint, allowing an attacker to inject carriage return and line feed (CRLF) characters into HTTP headers. By tricking a victim into visiting a crafted URL, an attacker can perform HTTP response splitting, leading to the addition of a new administrative user with full permissions. This effectively grants the attacker complete control over the device. The vulnerability has a CVSS score of 6.5 (Medium), but the impact is severe due to the potential for full device takeover. A patch is available in KeeneticOS 4.3.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in KeeneticOS, affecting the embedded web server and authentication API.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• Attack Vector (AV): Network – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): None – No authentication is needed to trigger the injection.
• User Interaction (UI): Required – The victim must click a crafted link or visit a malicious page.
• Scope (S): Unchanged – The exploit affects only the vulnerable component.
• Confidentiality (C): High – An attacker can gain full access to device data.
• Integrity (I): High – An attacker can modify device configuration and add users.
• Availability (A): High – An attacker could potentially disrupt device operation.

Threat Level: High. While the CVSS score is Medium, the real-world impact is severe due to the ability to achieve persistent, privileged access to the device.

Deep Dive & Mechanics

The vulnerability is a classic CRLF injection (CWE-93) in the /auth API endpoint of KeeneticOS. The endpoint is used for authentication and likely processes user-supplied input (e.g., username, password, or redirect parameters) without proper sanitization.

How it works:

1. The /auth endpoint accepts HTTP requests with parameters that are reflected in the HTTP response headers.
2. An attacker crafts a malicious URL containing CRLF sequences (%0d%0a or \r\n) followed by arbitrary HTTP headers and body content.
3. When the victim visits this URL, the server's response is split into two separate HTTP responses.
4. The second response, controlled by the attacker, can set arbitrary cookies, redirect the browser, or, in this case, execute a script that adds a new administrative user to the device.
5. The attacker can then log in with the newly created credentials and take full control of the Keenetic device.

Example Attack Flow:

1. Attacker crafts a URL like: http://<router-ip>/auth?redirect=%0d%0aHTTP/1.1%20200%20OK%0d%0aContent-Type:%20text/html%0d%0a%0d%0a<script>fetch('/auth',{method:'POST',headers:{'Content-Type':'application/x-www-form-urlencoded'},body:'username=hacker&password=hacked&role=admin'})</script>
2. Victim clicks the link.
3. The server interprets the CRLF and sends two responses. The browser processes the second response as a new page.
4. The JavaScript in the second response executes, sending a POST request to /auth to create a new user.
5. The attacker now has admin access.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

# Vulnerable Python-like pseudocode
def handle_auth(request):
    redirect_url = request.GET.get('redirect', '/')
    response = HttpResponseRedirect(redirect_url)
    return response

The redirect_url is directly used in the Location header without sanitization, allowing CRLF injection.

Patched Code (Conceptual):

# Patched Python-like pseudocode
import re

def handle_auth(request):
    redirect_url = request.GET.get('redirect', '/')
    # Sanitize: remove any CRLF characters
    sanitized_url = re.sub(r'[\r\n]', '', redirect_url)
    response = HttpResponseRedirect(sanitized_url)
    return response

The patched code removes any CRLF characters from the input before using it in the response header.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A Keenetic device running KeeneticOS < 4.3.
• A victim machine (e.g., a browser on the same network).
• A web server to host the exploit page (optional, for social engineering).

Exploit Steps:

1. Craft the Malicious URL: Replace <router-ip> with the target device's IP address.

   http://<router-ip>/auth?redirect=%0d%0aHTTP/1.1%20200%20OK%0d%0aContent-Type:%20text/html%0d%0a%0d%0a<script>fetch('/auth',{method:'POST',headers:{'Content-Type':'application/x-www-form-urlencoded'},body:'username=attacker&password=attacker123&role=admin'})</script>
   

2. Deliver the URL:

   • Send the URL to the victim via email, messaging, or a phishing page.
   • Alternatively, host a page that auto-redirects to the crafted URL.

3. Execute:

   • The victim clicks the link.
   • The browser processes the injected response and executes the JavaScript.
   • A new user attacker with password attacker123 and admin role is created.

4. Takeover:

   • Log in to the Keenetic web interface using the new credentials.
   • Change settings, exfiltrate data, or pivot to other devices on the network.

No Exploit-DB code was provided.

Blue Team (Defensive)

Detection:

• Monitor HTTP requests to /auth for unusual parameters containing %0d%0a or \r\n.
• Look for multiple Set-Cookie or Location headers in a single response.
• Alert on the creation of new users, especially with admin privileges, outside of normal administrative activity.

Prevention:

• Apply the vendor patch immediately (upgrade to KeeneticOS 4.3).
• Implement a Web Application Firewall (WAF) rule to block CRLF sequences in request parameters.
• Restrict access to the Keenetic web interface to trusted IP addresses only.
• Educate users not to click on suspicious links, especially those containing IP addresses or unusual characters.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /auth containing %0d%0a or \r\n in the query string.
  • HTTP responses from the Keenetic device with multiple Set-Cookie or Location headers.
  • Unusual POST requests to /auth with parameters like username, password, and role.
• Host IOCs (on the Keenetic device):
  • New user accounts in the system configuration that were not created by an administrator.
  • Unusual entries in the device logs indicating user creation or authentication from unknown IPs.
• File IOCs:
  • Modified configuration files (e.g., /etc/config/users or similar) containing unauthorized user entries.

Detection Engineering

YARA Rule

rule CVE_2025_56007_CRLF_Injection {
    meta:
        description = "Detects CRLF injection attempts targeting KeeneticOS /auth endpoint"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-56007"
        severity = "high"
    strings:
        $crlf1 = "%0d%0a"
        $crlf2 = "%0D%0A"
        $crlf3 = "\\r\\n"
        $auth_path = "/auth"
        $user_creation = "username="
        $role_admin = "role=admin"
    condition:
        any of ($crlf*) and $auth_path and (all of ($user_creation, $role_admin))
}

Sigma Rule

title: KeeneticOS CRLF Injection Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests to KeeneticOS /auth endpoint containing CRLF sequences
author: Valters IT
date: 2025/04/10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-56007
logsource:
    category: webserver
    product: keenetic
detection:
    selection:
        cs-uri-query|contains:
            - '%0d%0a'
            - '%0D%0A'
            - '\\r\\n'
        cs-uri-stem: '/auth'
    condition: selection
falsepositives:
    - Legitimate use of encoded characters in other contexts (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-56007 KeeneticOS CRLF Injection Attempt";
    flow:to_server,established;
    content:"/auth"; http_uri;
    content:"%0d%0a"; http_uri;
    content:"username="; http_uri;
    content:"role=admin"; http_uri;
    classtype:attempted-admin;
    sid:10000001;
    rev:1;
    reference:cve,2025-56007;
)

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade all Keenetic devices to KeeneticOS version 4.3 or later. This is the only complete fix.
2. Workaround: If patching is not immediately possible, restrict access to the web interface to trusted IP addresses only using firewall rules.
3. Monitor: Review device logs for any signs of unauthorized user creation or suspicious authentication attempts.

Long-Term Measures:

• Implement a Web Application Firewall (WAF) with rules to block CRLF injection attempts.
• Conduct regular security audits of all network devices.
• Ensure that all firmware and software are kept up-to-date.
• Educate users about the risks of clicking on unsolicited links.

Valters IT