CVE-2025-27909
📋 TL;DR
IBM Concert Software versions 1.0.0 through 1.1.0 have an overly permissive CORS configuration that doesn't restrict allowed origins to trusted domains. This allows attackers to perform cross-origin requests that could lead to unauthorized privileged actions. Organizations running affected IBM Concert Software versions are vulnerable.
💻 Affected Systems
- IBM Concert Software
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An attacker could perform administrative actions, modify data, or access sensitive information by tricking authenticated users into visiting malicious websites that make cross-origin requests to the vulnerable Concert instance.
Likely Case
Attackers could perform unauthorized actions within the application's context, potentially modifying user data or application settings through CSRF-like attacks.
If Mitigated
With proper CORS restrictions, only trusted domains can make cross-origin requests, preventing unauthorized access from malicious sites.
🎯 Exploit Status
Exploitation requires an attacker to trick an authenticated user into visiting a malicious website. The attack leverages the browser's same-origin policy bypass.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 1.1.1 or later
Vendor Advisory: https://www.ibm.com/support/pages/node/7242354
Restart Required: No
Instructions:
1. Download IBM Concert Software version 1.1.1 or later from IBM support portal. 2. Follow IBM's upgrade documentation for your deployment type. 3. Verify the CORS configuration now restricts origins to trusted domains only.
🔧 Temporary Workarounds
Configure CORS Restrictions
allManually configure CORS to only allow trusted domains. This restricts cross-origin requests to approved origins only.
Consult IBM Concert documentation for CORS configuration specific to your deployment
Implement Reverse Proxy CORS Controls
allUse a reverse proxy (like nginx or Apache) to enforce CORS restrictions before requests reach the vulnerable application.
Add CORS headers configuration to reverse proxy: add_header 'Access-Control-Allow-Origin' 'trusted-domain.com';
add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
🧯 If You Can't Patch
- Implement strict CORS policies at the web server or reverse proxy level to only allow trusted domains
- Use network segmentation to isolate IBM Concert instances and restrict access to trusted networks only
🔍 How to Verify
Check if Vulnerable:
Check if 'Access-Control-Allow-Origin' header is set to '*' or includes untrusted domains when making cross-origin requests to the Concert application.Check Version:
Check IBM Concert administration interface or consult deployment documentation for version informationVerify Fix Applied:
Verify that cross-origin requests from untrusted domains are rejected with appropriate CORS error responses, and only trusted domains are allowed.📡 Detection & Monitoring
Log Indicators:
- Multiple failed CORS preflight requests from unusual domains
- Unexpected cross-origin requests in application logs
- Requests with 'Origin' headers from non-approved domains
Network Indicators:
- CORS preflight OPTIONS requests to Concert endpoints from unusual domains
- Cross-origin POST/GET requests with authentication cookies
SIEM Query:
source="concert_logs" AND (http_method="OPTIONS" AND uri="*" AND origin!="trusted-domain*") OR (http_method="POST" AND referer!="trusted-domain*")