CVE-2025-65782

Executive Summary

CVE-2025-65782 is an authorization vulnerability in Wekan, the open-source kanban board system, affecting versions up to 18.15. The flaw resides in the card update handling mechanism, allowing board members and potentially other authenticated users to manipulate the vote.positive and vote.negative arrays of any card. This enables vote forgery and unauthorized voting, undermining the integrity of the voting system. The vulnerability is fixed in version 18.16.

Supply Chain & Package Security

Wekan is a Node.js application distributed via GitHub and Docker. The vulnerability is in the application logic, not in a direct dependency. However, users should verify the integrity of their Wekan installation and ensure they are running the patched version (18.16) from a trusted source.

CVSS Breakdown & Threat Level

The CVSS score is not provided in the NVD data. However, based on the description, a reasonable assessment would be:

• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): Low (L) – An attacker needs to be an authenticated user with board member privileges.
• User Interaction (UI): None (N) – No user interaction is required.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): None (N) – No data is exposed.
• Integrity (I): High (H) – The attacker can manipulate voting data.
• Availability (A): None (N) – No impact on availability.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N Estimated Base Score: 6.5 (Medium)

Threat Level: Medium. The vulnerability requires authentication but allows an attacker to manipulate voting results, which could be used to influence decisions or cause reputational damage.

Deep Dive & Mechanics

The vulnerability is an authorization flaw in the card update API endpoint. When a user updates a card, the server does not properly validate whether the user has the right to modify the vote.positive and vote.negative arrays. This allows any board member (or potentially any authenticated user) to add or remove arbitrary user IDs from these arrays.

Root Cause: The server-side code fails to check if the user performing the update is the owner of the vote or has the necessary permissions to modify the voting data. The vote arrays are treated as regular card fields without proper authorization checks.

Attack Vector: An authenticated user can send a crafted HTTP request to the card update endpoint, including malicious data in the vote.positive or vote.negative fields. The server will accept these changes without verifying the user's authorization.

Impact: An attacker can:

• Add fake votes to a card (vote forgery).
• Remove legitimate votes from a card.
• Manipulate the outcome of any voting process on the board.

Vulnerable vs. Patched Code

Vulnerable Code (Pre-18.16): The vulnerable code likely resides in the card update handler. A simplified example:

// Vulnerable: No authorization check on vote arrays
Meteor.methods({
  'cards.update': function(cardId, modifier) {
    // ... other checks ...
    Cards.update(cardId, modifier);
  }
});

Patched Code (18.16): The patched code adds authorization checks to ensure only the vote owner or authorized users can modify the vote arrays.

// Patched: Authorization check on vote arrays
Meteor.methods({
  'cards.update': function(cardId, modifier) {
    // ... other checks ...
    if (modifier.$set && (modifier.$set['vote.positive'] || modifier.$set['vote.negative'])) {
      // Check if the user is authorized to modify votes
      if (!this.userId || !isVoteAuthorized(this.userId, cardId)) {
        throw new Meteor.Error('not-authorized');
      }
    }
    Cards.update(cardId, modifier);
  }
});

Exploitation & Lab Setup

Red Team

Prerequisites:

• Access to a Wekan instance (version < 18.16).
• Valid user credentials with board member privileges.

Exploitation Steps:

1. Identify the target card: Find the card ID you want to manipulate. This can be obtained from the board's API or by inspecting the page source.

2. Craft the malicious request: Use a tool like curl or Burp Suite to send a request to the card update endpoint.

   curl -X POST \
     -H "Content-Type: application/json" \
     -H "Cookie: <your_session_cookie>" \
     -d '{
       "cardId": "<target_card_id>",
       "modifier": {
         "$set": {
           "vote.positive": ["<attacker_user_id>", "<victim_user_id>"],
           "vote.negative": []
         }
       }
     }' \
     http://<wekan_url>/api/cards/update
   

3. Verify the attack: Check the card's voting data to confirm the manipulation.

Blue Team

Detection:

• Monitor API logs for unusual card update requests, especially those modifying vote.positive or vote.negative fields.
• Look for requests where the user ID in the vote arrays does not match the authenticated user.

Prevention:

• Immediately upgrade to Wekan version 18.16 or later.
• Implement additional logging and alerting for card update operations.
• Review user permissions and ensure the principle of least privilege is applied.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests to /api/cards/update with vote.positive or vote.negative in the request body.
  • Unusual patterns of card updates from a single user.

• System IOCs:

  • Log entries showing card updates with modified vote arrays.
  • Discrepancies between expected and actual voting data on cards.

• File IOCs:

  • Modified database entries in the cards collection showing unauthorized vote changes.

Detection Engineering

YARA Rule

rule Detect_Vote_Forgery_Request {
  meta:
    description = "Detects HTTP requests attempting to forge votes in Wekan"
    author = "Valters IT"
    date = "2025-04-10"
    reference = "CVE-2025-65782"
  strings:
    $vote_positive = "vote.positive"
    $vote_negative = "vote.negative"
    $card_update = "/api/cards/update"
  condition:
    all of them
}

Sigma Rule

title: Wekan Vote Forgery Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to exploit CVE-2025-65782 by modifying vote arrays in Wekan
author: Valters IT
date: 2025-04-10
logsource:
  category: webserver
  product: nginx
detection:
  selection:
    cs-method: 'POST'
    cs-uri-stem: '/api/cards/update'
    cs-uri-query|contains: 
      - 'vote.positive'
      - 'vote.negative'
  condition: selection
falsepositives:
  - Legitimate vote modifications by authorized users
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
  msg:"CVE-2025-65782 Wekan Vote Forgery Attempt";
  flow:to_server,established;
  content:"POST"; http_method;
  content:"/api/cards/update"; http_uri;
  content:"vote.positive"; http_client_body;
  content:"vote.negative"; http_client_body;
  classtype:attempted-admin;
  sid:1000001;
  rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Upgrade Wekan: Update to version 18.16 or later immediately.
2. Verify Integrity: After upgrade, verify the integrity of the voting data on all boards.
3. Review Logs: Check server logs for any signs of exploitation.

Long-term Mitigations:

• Implement strict authorization checks for all card update operations.
• Use input validation to ensure only authorized users can modify vote arrays.
• Enable audit logging for all card modifications.
• Regularly review and update user permissions.

Workarounds (if upgrade is not possible):

• Disable the voting feature temporarily.
• Implement a reverse proxy to block requests containing vote.positive or vote.negative in the request body.

Valters IT