CVE-2025-36153: IBM Concert XSS Vulnerability

CVE-2025-36153 Overview

CVE-2025-36153 is a reflected cross-site scripting (XSS) vulnerability affecting IBM Concert versions 1.0.0 through 2.0.0. The flaw allows an unauthenticated attacker to embed arbitrary JavaScript code in the Web UI. Successful exploitation alters the intended functionality of the application within a trusted session. Attackers can leverage the injected script to disclose credentials or hijack authenticated user sessions.

The vulnerability is categorized under CWE-79 (Improper Neutralization of Input During Web Page Generation). Exploitation requires user interaction, such as clicking a crafted link, but does not require prior authentication to the target application.

Critical Impact
An unauthenticated attacker can inject JavaScript into the IBM Concert Web UI, enabling credential theft and session compromise within a trusted user context.

Affected Products

IBM Concert 1.0.0
IBM Concert versions 1.0.0 through 2.0.0
IBM Concert 2.0.0

Discovery Timeline

2025-11-20 - CVE-2025-36153 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-36153

Vulnerability Analysis

The vulnerability resides in the IBM Concert Web UI, which fails to properly neutralize user-supplied input before rendering it in served HTML pages. An attacker can craft a request containing malicious JavaScript payloads that the application reflects back to the browser without sufficient encoding or sanitization.

Because the scope is changed (S:C in the CVSS vector), injected script executes in a security context beyond the vulnerable component, expanding the potential blast radius. The confidentiality and integrity impacts are limited but sufficient to steal session tokens, cookies, or form data submitted through the Web UI.

Exploitation requires user interaction. A victim must click a crafted URL or visit an attacker-controlled page that triggers the request against a vulnerable IBM Concert instance.

Root Cause

The root cause is improper neutralization of input during web page generation, classified as [CWE-79]. IBM Concert does not enforce contextual output encoding on parameters reflected into the Web UI. This allows script tags, event handlers, or JavaScript URIs supplied by an attacker to execute in the victim's browser.

Attack Vector

The attack vector is network-based with low complexity. An attacker crafts a malicious link containing an XSS payload targeted at an IBM Concert endpoint. The attacker delivers the link through phishing, forum posts, or embedded content. When an authenticated Concert user clicks the link, the injected script runs in their browser and can exfiltrate session cookies, capture keystrokes, or perform actions on behalf of the user.

The vulnerability manifests when reflected parameters are rendered without HTML entity encoding. See the IBM Support Page for authoritative technical details.

Detection Methods for CVE-2025-36153

Indicators of Compromise

Web server access logs containing URL parameters with <script>, javascript:, onerror=, or onload= payloads directed at IBM Concert endpoints.
Unexpected outbound HTTP requests from user browsers to attacker-controlled domains following interaction with Concert URLs.
Anomalous session token reuse from geographically or temporally inconsistent client IP addresses.

Detection Strategies

Deploy web application firewall (WAF) rules that inspect query strings and POST bodies for common XSS payload signatures targeting Concert URIs.
Enable browser-side Content Security Policy (CSP) violation reporting to identify inline script execution attempts.
Correlate authentication events with Referer headers to identify sessions initiated from suspicious external redirectors.

Monitoring Recommendations

Monitor IBM Concert web access logs for URL-encoded script tags and JavaScript event handler patterns.
Alert on user sessions where session tokens appear in URL parameters or Referer headers sent to external hosts.
Track spikes in HTTP 4xx responses from Concert endpoints, which may indicate payload probing activity.

How to Mitigate CVE-2025-36153

Immediate Actions Required

Apply the IBM security update referenced in the IBM Support Page advisory for IBM Concert.
Restrict access to the Concert Web UI to trusted network segments until patching is complete.
Instruct Concert users to avoid clicking untrusted links referencing the Concert application hostname.

Patch Information

IBM has published remediation guidance for CVE-2025-36153 on the official IBM Support Page. Administrators should upgrade IBM Concert to the fixed release identified in the advisory. Verify version strings after patching to confirm the deployment is no longer within the vulnerable 1.0.0 through 2.0.0 range.

Workarounds

Enforce a strict Content Security Policy that disallows inline script execution and restricts script sources to trusted origins.
Configure the reverse proxy or WAF to reject requests containing HTML control characters in query parameters destined for Concert endpoints.
Require re-authentication for sensitive Concert actions to limit the value of stolen session cookies.

bash

# Example nginx configuration to add a restrictive CSP header for IBM Concert
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'none'" always;
add_header X-XSS-Protection "1; mode=block" always;
add_header X-Content-Type-Options "nosniff" always;