CVE-2025-67809

Executive Summary

CVE-2025-67809 exposes a critical security flaw in Zimbra Collaboration (ZCS) versions 10.0 and 10.1. A hardcoded Flickr API key and secret were discovered within the publicly accessible Flickr Zimlet. This embedded credential allows any unauthorized party to retrieve it and misuse the Flickr integration. An attacker could impersonate the legitimate Zimbra application, initiate valid OAuth flows, and, if a user is tricked into approving the request, gain unauthorized access to the user's Flickr data. The vulnerability has been addressed by removing the hardcoded credentials from the Zimlet code and revoking the associated key.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a direct code-level issue within the Zimbra Collaboration Suite's Zimlet component.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or indicates that the score has not been officially calculated. However, based on the nature of the vulnerability (hardcoded credentials in a publicly accessible component), the potential impact is significant.

• Attack Vector (AV): Network (the Zimlet is accessible over the network)
• Attack Complexity (AC): Low (the credentials are hardcoded and easily retrievable)
• Privileges Required (PR): None (the Zimlet is publicly accessible)
• User Interaction (UI): Required (the attacker must trick a user into approving an OAuth flow)
• Scope (S): Changed (the attacker gains access to a third-party service, Flickr)
• Confidentiality (C): High (user's Flickr data could be exposed)
• Integrity (I): High (attacker could modify or delete Flickr data)
• Availability (A): Low (unlikely to affect availability directly)

Threat Level: High. The ease of exploitation (hardcoded credentials) combined with the potential for data theft makes this a serious concern for Zimbra users who have integrated Flickr.

Deep Dive & Mechanics

The vulnerability stems from a fundamental security anti-pattern: embedding API credentials directly in client-side code. The Flickr Zimlet, a component of Zimbra Collaboration, contained a hardcoded Flickr API key and secret. Because Zimlets are loaded and executed in the user's browser, any user (or attacker) can inspect the Zimlet's source code and extract these credentials.

Attack Flow:

1. Discovery: An attacker accesses the Zimbra web interface and inspects the Flickr Zimlet's JavaScript or configuration files to extract the hardcoded API key and secret.
2. Impersonation: Using the stolen credentials, the attacker can initiate an OAuth flow with Flickr, impersonating the legitimate Zimbra application.
3. Phishing: The attacker crafts a phishing email or social engineering attack that tricks a Zimbra user into clicking a link that initiates the OAuth authorization request.
4. Authorization: If the user approves the request, the attacker receives an OAuth token that grants them access to the user's Flickr account.
5. Data Exfiltration: The attacker can now access, modify, or delete the user's Flickr photos, albums, and other data.

Vulnerable vs. Patched Code

Vulnerable Code (Zimbra Collaboration 10.0, 10.1): The vulnerable code would contain hardcoded strings for the Flickr API key and secret. For example, in a JavaScript file:

// Vulnerable Zimlet code
var flickrApiKey = "YOUR_HARDCODED_API_KEY";
var flickrApiSecret = "YOUR_HARDCODED_API_SECRET";

Patched Code: The patched code removes these hardcoded values and instead uses a server-side proxy or a configuration mechanism that does not expose the credentials to the client. For example:

// Patched Zimlet code
// Credentials are no longer hardcoded; they are fetched from a secure server-side endpoint
fetch('/api/flickr/credentials')
  .then(response => response.json())
  .then(data => {
    // Use data.apiKey and data.apiSecret securely
  });

Exploitation & Lab Setup

Red Team (Attacker) Perspective

Objective: Extract hardcoded Flickr credentials and attempt to gain unauthorized access to a user's Flickr account.

Lab Setup:

1. Environment: A Zimbra Collaboration 10.0 or 10.1 instance with the Flickr Zimlet enabled.
2. Tools: Web browser with developer tools (e.g., Chrome DevTools), curl, or a simple HTTP client.

Steps:

1. Access Zimbra Web Client: Log in to the Zimbra web interface.
2. Inspect Zimlet: Navigate to the page where the Flickr Zimlet is loaded. Use browser developer tools to view the source code of the Zimlet's JavaScript files.
3. Extract Credentials: Search for strings like "api_key", "api_secret", "flickr", or similar patterns. The hardcoded values will be present in plaintext.
4. Initiate OAuth Flow: Use the extracted credentials to construct a valid Flickr OAuth request URL. For example:

   https://www.flickr.com/services/oauth/authorize?oauth_token=REQUEST_TOKEN&perms=read
   

5. Phish User: Send a crafted email to a Zimbra user with a link to the above URL, tricking them into authorizing the application.
6. Gain Access: Once the user authorizes, capture the OAuth verifier and exchange it for an access token. Use this token to access the user's Flickr data via the Flickr API.

Blue Team (Defender) Perspective

Objective: Detect and prevent exploitation of hardcoded credentials.

Detection Steps:

1. Code Review: Regularly audit Zimlet code for hardcoded secrets. Use static analysis tools to scan for patterns like api_key, secret, password, etc.
2. Network Monitoring: Monitor for unusual OAuth flows to Flickr originating from the Zimbra server. Look for requests to flickr.com/services/oauth/ that do not originate from expected user interactions.
3. User Education: Train users to be cautious of OAuth authorization requests, especially those that appear to come from Zimbra but request access to external services.
4. Patch Management: Apply the latest Zimbra patches immediately. The vendor has removed the hardcoded credentials and revoked the key.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Unusual outbound connections to api.flickr.com or flickr.com from the Zimbra server.
  • OAuth callback URLs containing the hardcoded API key (if not revoked).
• File IOCs:
  • Presence of hardcoded Flickr API key and secret in Zimlet JavaScript files (e.g., flickrZimlet.js).
• Behavioral IOCs:
  • Multiple failed OAuth authorization attempts from the same IP address.
  • User reports of unauthorized access to their Flickr accounts.

Detection Engineering

YARA Rule

rule CVE_2025_67809_Hardcoded_Flickr_Credentials {
    meta:
        description = "Detects hardcoded Flickr API key and secret in Zimbra Zimlet files"
        author = "Valters IT"
        date = "2025-01-01"
        reference = "CVE-2025-67809"
    strings:
        $api_key = /flickrApiKey\s*=\s*["'][A-Za-z0-9]+["']/ nocase
        $api_secret = /flickrApiSecret\s*=\s*["'][A-Za-z0-9]+["']/ nocase
    condition:
        any of them
}

Sigma Rule

title: Detection of Hardcoded Flickr Credentials in Zimbra Zimlet
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects attempts to access or extract hardcoded Flickr API credentials from Zimbra Zimlet files.
author: Valters IT
date: 2025/01/01
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\powershell.exe'
        CommandLine|contains: 'flickrApiKey'
    condition: selection
falsepositives:
    - Legitimate development activities
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-67809 - Hardcoded Flickr Credentials Exfiltration"; flow:to_server,established; content:"flickrApiKey"; http_client_body; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Patch Zimbra: Apply the latest Zimbra Collaboration update that removes the hardcoded credentials. The vendor has revoked the associated key.
2. Revoke Access: If any users have authorized the old Flickr application, instruct them to revoke access in their Flickr account settings.
3. Audit Logs: Review Zimbra and Flickr logs for any signs of unauthorized access.

Long-Term Mitigations:

1. Secure Credential Storage: Never hardcode API keys or secrets in client-side code. Use server-side proxies or secure vaults.
2. Regular Code Audits: Implement automated scanning for hardcoded secrets in all Zimlet and application code.
3. User Awareness: Educate users about the risks of OAuth phishing and how to verify legitimate authorization requests.
4. Network Segmentation: Restrict outbound access from the Zimbra server to only necessary services.

Valters IT