CVE-2024-6939

Executive Summary

CVE-2024-6939 identifies a Cross-Site Scripting (XSS) vulnerability in Xinhu RockOA version 2.6.3, specifically within the tpl_upload.html file's okla function. This flaw allows a remote attacker to inject malicious scripts via the callback argument, leading to potential client-side compromise. Given that an exploit has been publicly disclosed, immediate attention is warranted to mitigate risks to users interacting with vulnerable instances.

Technical Analysis

The vulnerability, classified as Cross-Site Scripting (XSS), resides within the Xinhu RockOA application, version 2.6.3. The specific affected component is the okla function, which is implemented in the /webmain/public/upload/tpl_upload.html file. This function is susceptible to improper input sanitization or output encoding when processing the callback argument.

An attacker can exploit this flaw by crafting a malicious URL that includes JavaScript code within the callback parameter. When a victim's browser accesses this specially crafted URL, the tpl_upload.html page processes the unsanitized callback argument, leading to the execution of the injected script within the victim's browser context. This client-side execution occurs with the privileges and cookies of the victim's active session on the RockOA application.

The vulnerability is directly tied to the lack of sufficient input validation and/or output encoding for the callback parameter before its content is rendered back into the HTML response. This allows for a reflected XSS attack where the malicious payload is part of the request and reflected by the server without proper neutralization, causing the browser to interpret it as legitimate script. The attack vector is remote, implying that an attacker does not require direct access to the server or specific administrative privileges within RockOA, only the ability to trick a user into clicking a malicious link or visiting a compromised page that embeds such a link.

Exploitation Scenarios

Exploitation of CVE-2024-6939 involves a classic reflected Cross-Site Scripting (XSS) attack chain, leveraging the improper handling of user-supplied input by the Xinhu RockOA application.

1. Reconnaissance/Target Identification: An attacker identifies publicly accessible instances of Xinhu RockOA running version 2.6.3. This can be achieved through various methods, including Shodan queries for "RockOA" or "Xinhu RockOA" keywords in http.html or http.title, or by direct enumeration of web applications within a target organization. The attacker then identifies the vulnerable endpoint: /webmain/public/upload/tpl_upload.html.

2. Triggering the Specific Flaw: The attacker crafts a malicious URL designed to exploit the XSS vulnerability. This URL will target the /webmain/public/upload/tpl_upload.html endpoint and include a specially constructed callback argument containing the malicious JavaScript payload. For example, a URL might look like: http://[rockoa_host]/webmain/public/upload/tpl_upload.html?callback=<script>alert('XSS')</script>. The okla function within tpl_upload.html is responsible for processing this callback parameter without adequate sanitization.

3. Payload/Execution Method: The crafted URL, containing the malicious callback parameter, is then delivered to a target user. This social engineering step typically involves phishing emails, malicious advertisements, or embedded links on compromised websites. When the victim clicks the link, their browser makes a request to the vulnerable RockOA instance. The RockOA server, specifically the okla function in tpl_upload.html, reflects the unsanitized callback parameter's content directly into the HTML response. The victim's browser then interprets and executes the embedded JavaScript code as legitimate content from the trusted RockOA domain.

4. Post-Exploitation Impact: Upon successful execution of the injected JavaScript, the attacker can achieve various post-exploitation objectives, depending on the payload. Common impacts include:

   • Session Hijacking: Stealing session cookies, allowing the attacker to impersonate the victim and access their RockOA account without credentials.
   • Defacement: Modifying the content of the web page visible to the victim.
   • Data Theft: Exfiltrating sensitive information displayed on the page or accessible via JavaScript (e.g., CSRF tokens, user-specific data) to an attacker-controlled server.
   • Further Client-Side Attacks: Redirecting the user to a malicious website, initiating downloads of malware, or performing arbitrary actions on the user's behalf within the RockOA application (e.g., changing settings, sending messages) by making AJAX requests.
   • Worming: In highly interactive applications, an XSS payload might spread itself to other users, potentially leading to a widespread compromise.

The exploit has been publicly disclosed, which increases the likelihood of this attack vector being utilized by opportunistic threat actors.

Impact Assessment

The impact of CVE-2024-6939 is significant, primarily affecting the confidentiality and integrity of user data and the overall trust in the Xinhu RockOA application. With a CVSS base score of 5.3, this vulnerability is classified as medium severity, but its real-world impact can be higher due to the nature of XSS.

Confidentiality (C:L - Low): An attacker can potentially steal sensitive information accessible to the victim's browser, such as session cookies, allowing for session hijacking. This could lead to unauthorized access to the victim's RockOA account and any data associated with it. While direct server-side data exfiltration is not possible via XSS, client-side data available in the DOM or via JavaScript APIs could be compromised.

Integrity (I:L - Low): The attacker can manipulate the content displayed to the victim, leading to website defacement or misleading information. More critically, the attacker can perform actions on behalf of the victim within the RockOA application if the application relies on client-side requests (e.g., making internal API calls with the victim's session). This could lead to unauthorized modifications of settings, data, or content.

Availability (A:N - None): This vulnerability does not directly impact the availability of the Xinhu RockOA service. The application itself will remain operational, although individual user experiences may be disrupted by malicious scripts.

Attack Vector (AV:N - Network): The vulnerability is exploitable over the network, meaning an attacker does not need local access or specific network proximity to the target server. This broadens the potential attack surface significantly.

Attack Complexity (AC:L - Low): Exploiting this vulnerability is relatively straightforward once an attacker understands the mechanism. It primarily involves crafting a malicious URL and tricking a user into clicking it.

Privileges Required (PR:N - None): An attacker does not need any specific privileges or authentication to exploit this vulnerability. The attack targets an unauthenticated endpoint or a page that reflects user input without authentication.

User Interaction (UI:R - Required): Successful exploitation requires user interaction, typically in the form of clicking a malicious link. This reduces the fully automated nature of the attack but is a common characteristic of reflected XSS vulnerabilities.

Scope (S:C - Changed): The scope is changed because the attacker's payload executes in the context of the vulnerable application's domain, allowing the script to bypass the Same-Origin Policy and potentially impact other resources within that domain.

The blast radius extends to any user interacting with a vulnerable Xinhu RockOA instance. Enterprise security teams should be particularly concerned about the potential for session hijacking, which could lead to compromised user accounts, internal data breaches, and a foothold for further attacks within an organization's internal network if RockOA is used for internal operations.

Detection Guidance

Effective detection for CVE-2024-6939 focuses on identifying HTTP requests that exhibit characteristics of XSS payloads targeting the specific vulnerable endpoint and parameter. Monitoring web server logs, proxy logs, and network traffic for unusual patterns in the callback parameter of requests to /webmain/public/upload/tpl_upload.html is crucial.

Sigma Rule

title: Xinhu RockOA tpl_upload.html XSS Attempt (CVE-2024-6939)
id: 5b4e7a3c-9d1f-4c2d-8e5b-f7a1d3e8c9b2
status: experimental
description: Detects attempts to exploit CVE-2024-6939, an XSS vulnerability in Xinhu RockOA 2.6.3
    via the 'callback' parameter in tpl_upload.html.
author: valtersit.com
date: 2024/07/26
logsource:
  category: webserver
  service: access_log
detection:
  selection:
    cs-uri-stem|contains: '/webmain/public/upload/tpl_upload.html'
    cs-uri-query|contains:
      - 'callback='
      - '<script>'
      - 'javascript:'
      - 'onerror='
      - 'onload='
      - 'confirm('
      - 'alert('
      - 'prompt('
      - '%3cscript%3e' # URL-encoded <script>
      - '%20on'        # common for event handlers
      - '%3CIMG%20SRC%3D%22x%22%20onerror%3D%22'
  condition: selection
level: high
tags:
  - attack.injection
  - attack.xss
  - cve.2024.6939
  - product.xinhu
  - product.rockoa

YARA Rule

A YARA rule is typically used for file-based scanning, making it less direct for detecting live XSS attempts in web traffic or logs. However, a generic YARA rule could be crafted to scan collected log files or network captures (PCAPs) for patterns indicative of this XSS exploit. This rule focuses on identifying the specific path and common XSS payload components within textual data.

rule Xinhu_RockOA_CVE_2024_6939_XSS {
  meta:
    author = "valtersit.com"
    date = "2024-07-26"
    description = "Detects log entries or network captures related to CVE-2024-6939 XSS exploitation attempts."
    cve = "CVE-2024-6939"
    severity = "medium"
    product = "Xinhu RockOA"
    rule_type = "log_scan"
  strings:
    $path = "/webmain/public/upload/tpl_upload.html" ascii nocase
    $callback_param = "callback=" ascii nocase
    $script_tag1 = "<script>" ascii nocase
    $script_tag2 = "%3cscript%3e" ascii nocase
    $event_handler1 = "onerror=" ascii nocase
    $event_handler2 = "onload=" ascii nocase
    $alert_func = "alert(" ascii nocase
    $confirm_func = "confirm(" ascii nocase
    $prompt_func = "prompt(" ascii nocase
    $javascript_prefix = "javascript:" ascii nocase

  condition:
    $path and $callback_param and ($script_tag1 or $script_tag2 or $event_handler1 or $event_handler2 or $alert_func or $confirm_func or $prompt_func or $javascript_prefix)
}

Suricata IDS Rule

alert http any any -> any any (msg:"Xinhu RockOA CVE-2024-6939 XSS Attempt (tpl_upload.html callback)"; flow:to_server,established; http.uri; content:"/webmain/public/upload/tpl_upload.html"; http.uri; pcre:"/callback=(.*)(%3cscript%3e|<script>|javascript:|onerror=|onload=|alert\(|confirm\(|prompt\()/Usi"; classtype:web-application-attack; sid:2024693901; rev:1;)

Elastic Detection

{
  "query": {
    "bool": {
      "must": [
        {
          "wildcard": {
            "url.path": "*\/webmain\/public\/upload\/tpl_upload.html*"
          }
        },
        {
          "bool": {
            "should": [
              { "match_phrase": { "url.query": "callback=" } },
              { "wildcard": { "url.query": "*%3cscript%3e*" } },
              { "wildcard": { "url.query": "*<script>*" } },
              { "wildcard": { "url.query": "*javascript:*" } },
              { "wildcard": { "url.query": "*onerror=*" } },
              { "wildcard": { "url.query": "*onload=*" } },
              { "wildcard": { "url.query": "*alert(*" } },
              { "wildcard": { "url.query": "*confirm(*" } },
              { "wildcard": { "url.query": "*prompt(*" } }
            ]
          }
        }
      ]
    }
  },
  "language": "kuery"
}

Splunk SPL Query

sourcetype=access_combined (uri_path="/webmain/public/upload/tpl_upload.html" OR uri_path="*/webmain/public/upload/tpl_upload.html")
(uri_query="*callback=*" AND (uri_query="*%3cscript%3e*" OR uri_query="*<script>*" OR uri_query="*javascript:*" OR uri_query="*onerror=*" OR uri_query="*onload=*" OR uri_query="*alert(*" OR uri_query="*confirm(*" OR uri_query="*prompt(*"))
| table _time, clientip, uri_path, uri_query, useragent
| sort _time desc

Wazuh OSSEC Rule

Create a custom rule file (e.g., local_rules.xml) on your Wazuh manager.

<group name="web,app_attack,">
  <rule id="100001" level="10">
    <if_sid>31100</if_sid> <!-- Apache/Nginx access log decoded -->
    <url>/webmain/public/upload/tpl_upload.html</url>
    <options>pcrematch</options>
    <match type="regex" offset="after_url">callback=.*((%3cscript%3e)|(<script>)|(javascript:)|(onerror=)|(onload=)|(alert\()|(confirm\()|(prompt\()))</match>
    <description>Xinhu RockOA CVE-2024-6939 XSS Attempt detected in tpl_upload.html via callback parameter.</description>
    <group>attack,xss,cve,</group>
  </rule>
</group>

Remember to restart your Wazuh manager after adding custom rules (systemctl restart wazuh-manager). This rule assumes you have appropriate decoders for your web server logs configured (e.g., web-accesslog).

Mitigation & Patch Guidance

As of the current intelligence, Xinhu RockOA version 2.6.3 remains UNPATCHED for CVE-2024-6939. There is no available patch or vendor fix provided by Xinhu. This necessitates immediate focus on mitigation strategies to protect affected systems and users.

1. Immediate Mitigations:

   • Input Validation and Output Encoding (Server-Side): The most effective long-term mitigation, which should have been implemented by the vendor. For organizations with the capability, if custom modifications are possible, implement stringent server-side input validation on the callback parameter for /webmain/public/upload/tpl_upload.html. Additionally, ensure all user-supplied input is properly output-encoded (e.g., HTML entity encoding) before being rendered in the browser. This prevents malicious scripts from being executed.
   • Web Application Firewall (WAF): Deploy or configure a WAF to detect and block HTTP requests to /webmain/public/upload/tpl_upload.html that contain XSS payloads in the callback parameter. WAF rules should look for common XSS attack patterns such as <script>, javascript:, onerror=, onload=, and URL-encoded equivalents within the query string for this specific path.
   • Network Access Restrictions: If the /webmain/public/upload/tpl_upload.html endpoint is not intended for public access, restrict network access to only trusted IP ranges or internal networks using firewall rules. This reduces the attack surface.
   • Content Security Policy (CSP): Implement a strict Content Security Policy (CSP) on your web server. A well-configured CSP can significantly reduce the impact of XSS attacks by restricting which sources can execute scripts, load fonts, or submit forms. For instance, script-src 'self' would prevent scripts from external domains or inline scripts unless explicitly whitelisted.

2. Patch/Upgrade Steps:

   • Monitor Vendor Advisories: Continuously monitor the official Xinhu channels and security advisories for the release of a patch or an updated version of RockOA that addresses CVE-2024-6939. As soon as a fix is available, plan for an immediate upgrade or patch deployment.
   • Safe Upgrade Practices: When a patch becomes available, follow vendor-recommended upgrade procedures. Back up configurations and data before performing any updates. Test the patch in a staging environment if possible before deploying to production.

3. Long-Term Hardening:

   • Regular Security Audits: Conduct periodic security audits and penetration testing of all web applications, including Xinhu RockOA, to identify and remediate vulnerabilities proactively.
   • User Education: Educate users about the risks of phishing and clicking suspicious links, especially those that appear to come from internal applications.
   • Principle of Least Privilege: Ensure that the user accounts within RockOA have only the minimum necessary privileges, which can limit the impact of a session hijack.
   • Browser Security Settings: Encourage users to maintain updated browsers and utilize browser security features that offer protection against XSS (e.g., XSS filters, if still supported and active).

Given the public disclosure of exploitation details, organizations using Xinhu RockOA 2.6.3 should prioritize the implementation of the immediate mitigations outlined above until a vendor-supplied patch becomes available.

References

• NVD - CVE-2024-6939: https://nvd.nist.gov/vuln/detail/CVE-2024-6939
• VulDB - VDB-271994: https://vuldb.com/?id.271994
• Xinhu RockOA Project (General): http://www.rockoa.com/ (No specific advisory found for this CVE, general project link provided for context.)