CVE-2025-36560

Executive Summary

CVE-2025-36560 is a critical Server-Side Request Forgery (SSRF) vulnerability affecting multiple versions of a-blog cms. The flaw allows a remote, unauthenticated attacker to send specially crafted requests that force the server to make internal or external HTTP requests on behalf of the attacker. This can lead to unauthorized access to sensitive information, such as internal network resources, cloud metadata endpoints, or other backend services. The vulnerability has a CVSS score of 8.6 (High) and currently has no known public exploit or patch. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the risk remains significant due to the potential for information disclosure.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a standalone CMS product (a-blog cms) and does not involve a package manager supply chain.

CVSS Breakdown & Threat Level

• CVSS Score: 8.6 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

The high confidentiality impact combined with low attack complexity and no authentication requirement makes this a serious threat for any organization running a-blog cms. An attacker can probe internal networks, access cloud metadata (e.g., AWS, GCP), or retrieve sensitive files from the server.

Deep Dive & Mechanics

The vulnerability resides in the way a-blog cms handles user-supplied URLs or redirect parameters. When the application processes a request that includes a URL (e.g., for fetching external resources, proxying content, or following redirects), it does not properly validate the target host or protocol. An attacker can craft a request that points to internal IP addresses (e.g., http://169.254.169.254/ for cloud metadata) or localhost services (e.g., http://127.0.0.1:8080/admin).

The SSRF occurs because the application uses functions like file_get_contents(), curl_exec(), or similar HTTP clients without restricting the destination to a whitelist of allowed domains. The attacker can bypass any basic blocklists by using URL encoding, redirects, or alternative representations of IP addresses (e.g., decimal, octal, or IPv6 mapped IPv4).

Vulnerable vs. Patched Code

Since no official patch is available, the following is a conceptual comparison.

Vulnerable Code (PHP example):

<?php
$url = $_GET['url'];
$response = file_get_contents($url);
echo $response;
?>

Patched Code (Conceptual):

<?php
$url = $_GET['url'];
$parsed = parse_url($url);
$host = $parsed['host'];
$allowed = ['api.example.com', 'cdn.example.com'];
if (!in_array($host, $allowed)) {
    die('Invalid URL');
}
// Also block private IP ranges
if (filter_var($host, FILTER_VALIDATE_IP) && !filter_var($host, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE)) {
    die('Private IP not allowed');
}
$response = file_get_contents($url);
echo $response;
?>

Exploitation & Lab Setup

Red Team (Attack Simulation)

1. Setup: Deploy a vulnerable instance of a-blog cms (version 2.x or 3.x) in a lab environment. Ensure the server has network access to internal services (e.g., a local Redis, MySQL, or a cloud metadata simulator).
2. Craft Payload: Use a simple HTTP request to the vulnerable endpoint (e.g., /proxy.php?url=http://169.254.169.254/latest/meta-data/).
3. Execute: Send the request using curl:

   curl "http://target.com/proxy.php?url=http://169.254.169.254/latest/meta-data/"
   

4. Exfiltrate: The response will contain the cloud metadata (if on AWS) or internal service banners.

Blue Team (Detection & Hardening)

1. Network Segmentation: Ensure the web server cannot reach internal IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 127.0.0.0/8, 169.254.0.0/16).
2. WAF Rules: Deploy a Web Application Firewall (WAF) rule to block requests containing private IP addresses in URL parameters.
3. Input Validation: Implement strict allowlists for outbound HTTP requests from the application.
4. Monitor Logs: Look for outbound connections to unusual IPs or high volumes of requests to metadata endpoints.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound HTTP requests to 169.254.169.254, 127.0.0.1, 10.x.x.x, 172.16-31.x.x, 192.168.x.x.
  • Requests containing URL-encoded private IPs (e.g., %31%36%39%2e%32%35%34%2e%31%36%39%2e%32%35%34).
• File IOCs:
  • Log entries showing file_get_contents() or curl_exec() calls with suspicious URLs.
• Behavioral IOCs:
  • Unusual spikes in outbound HTTP traffic from the web server.
  • Access to cloud metadata endpoints from the CMS server.

Detection Engineering

YARA Rule

rule CVE_2025_36560_SSRF_Detection {
    meta:
        description = "Detects SSRF attempts targeting private IPs in a-blog cms"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-36560"
    strings:
        $private_ip1 = "169.254.169.254" ascii wide nocase
        $private_ip2 = "127.0.0.1" ascii wide nocase
        $private_ip3 = "10." ascii wide nocase
        $private_ip4 = "172.16." ascii wide nocase
        $private_ip5 = "192.168." ascii wide nocase
        $url_param = "url=" ascii wide nocase
    condition:
        any of ($private_ip*) and $url_param
}

Sigma Rule

title: CVE-2025-36560 SSRF Attempt Against a-blog cms
id: 8f7b3c2a-1d5e-4f6a-9b8c-0d1e2f3a4b5c
status: experimental
description: Detects HTTP requests to private IP addresses via URL parameters in a-blog cms
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-uri-query|contains:
            - 'url=http://169.254.169.254'
            - 'url=http://127.0.0.1'
            - 'url=http://10.'
            - 'url=http://172.16.'
            - 'url=http://192.168.'
    condition: selection
falsepositives:
    - Legitimate use of internal proxies (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-36560 SSRF Attempt - Private IP in URL"; flow:to_server; content:"url="; http_uri; pcre:"/url=http:\/\/(169\.254\.169\.254|127\.0\.0\.1|10\.|172\.(1[6-9]|2[0-9]|3[0-1])\.|192\.168\.)/i"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Mitigation:

   • Block outbound HTTP requests from the web server to private IP ranges using firewall rules.
   • Implement a reverse proxy or WAF to filter SSRF payloads.
   • Disable any unnecessary URL fetching functionality in the CMS.

2. Long-Term Fix:

   • Apply vendor patch when released.
   • Upgrade to a patched version of a-blog cms.
   • Conduct a code review to ensure all URL handling functions validate destinations against an allowlist.

3. Monitoring:

   • Enable detailed logging for all outbound HTTP requests.
   • Set up alerts for any requests to private IPs or cloud metadata endpoints.

Valters IT