CVE-2024-51451: IBM Concert HTTP Header Injection XSS

CVE-2024-51451 Overview

IBM Concert versions 1.0.0 through 2.1.0 contain an HTTP header injection vulnerability caused by improper validation of input by the HOST headers. This security flaw allows attackers to conduct various attacks against vulnerable systems, including cross-site scripting (XSS), cache poisoning, and session hijacking.

Critical Impact
Attackers can exploit improper HOST header validation to inject malicious content, potentially compromising user sessions and manipulating cached responses across the affected IBM Concert deployment.

Affected Products

IBM Concert 1.0.0
IBM Concert 1.0.1 through 2.0.x
IBM Concert 2.1.0

Discovery Timeline

2026-02-04 - CVE-2024-51451 published to NVD
2026-02-05 - Last updated in NVD database

Technical Details for CVE-2024-51451

Vulnerability Analysis

This vulnerability falls under CWE-644 (Improper Neutralization of HTTP Headers for Scripting Syntax), which occurs when an application does not properly neutralize or validate HTTP headers before they are used in scripted contexts. The vulnerability enables network-based attacks without requiring authentication or user interaction.

The flaw resides in IBM Concert's handling of HOST headers, where insufficient input validation allows attackers to inject arbitrary HTTP headers into responses. This can lead to multiple attack scenarios including XSS execution in victim browsers, web cache poisoning that affects all users of shared caches, and session hijacking through manipulated responses.

Root Cause

The root cause is improper validation of the HTTP HOST header input. When IBM Concert processes incoming HTTP requests, it fails to adequately sanitize or validate the HOST header values before incorporating them into server responses or internal processing logic. This lack of input validation allows specially crafted header values to be injected and interpreted in unintended ways.

Attack Vector

The attack vector is network-based, meaning an attacker can exploit this vulnerability remotely over HTTP/HTTPS connections. The attack does not require any privileges or user interaction, making it particularly accessible to opportunistic attackers.

An attacker can craft malicious HTTP requests with specially formatted HOST header values containing injected content such as additional headers, newline characters (CRLF), or script payloads. When the vulnerable IBM Concert instance processes these requests, the injected content may be reflected in responses, stored in caches, or used in ways that compromise security controls.

The vulnerability enables several attack types:

Cross-Site Scripting (XSS): Injected scripts execute in victim browsers
Cache Poisoning: Malicious responses are cached and served to other users
Session Hijacking: Manipulated headers interfere with session management

Detection Methods for CVE-2024-51451

Indicators of Compromise

Unusual or malformed HOST header values in web server access logs containing CRLF sequences (%0d%0a or \r\n)
HTTP responses containing unexpected headers or duplicate headers
Evidence of cache poisoning with responses that differ from legitimate application behavior
XSS payload signatures in HOST header fields within request logs

Detection Strategies

Implement web application firewall (WAF) rules to detect and block HTTP header injection attempts in HOST headers
Configure log monitoring to alert on requests containing CRLF sequences or other injection patterns in header fields
Deploy network intrusion detection signatures for HTTP header manipulation attacks
Review IBM Concert access logs for anomalous HOST header patterns that don't match expected domain names

Monitoring Recommendations

Enable detailed HTTP request logging on IBM Concert instances to capture full header content
Monitor for increased cache miss rates or cache inconsistencies that may indicate poisoning attempts
Set up alerts for XSS detection signatures in downstream security tools
Track session anomalies that could indicate hijacking attempts following header injection

How to Mitigate CVE-2024-51451

Immediate Actions Required

Upgrade IBM Concert to a patched version as specified in the vendor security advisory
Implement WAF rules to filter malicious HOST header values pending patch deployment
Review and restrict access to IBM Concert instances to trusted networks where possible
Enable enhanced logging to detect exploitation attempts

Patch Information

IBM has released a security update to address this vulnerability. Detailed patch information and installation instructions are available in the IBM Support Page. Organizations running IBM Concert versions 1.0.0 through 2.1.0 should apply the security update immediately.

Workarounds

Deploy a reverse proxy or WAF in front of IBM Concert to validate and sanitize HOST header values before they reach the application
Configure web servers to reject requests with malformed or unexpected HOST headers
Implement strict HOST header whitelisting at the network edge to only allow legitimate domain names
If feasible, restrict network access to IBM Concert instances to trusted internal networks until patching is complete

bash

# Example WAF rule concept for HOST header validation (implementation varies by WAF vendor)
# Block requests with CRLF injection attempts in HOST header
# Pattern: HOST header containing %0d, %0a, \r, or \n characters
SecRule REQUEST_HEADERS:Host "@rx (%0d|%0a|\\r|\\n)" "id:100001,phase:1,deny,status:403,msg:'HTTP Header Injection Attempt'"