CVE-2025-27901 Overview
IBM Db2 Recovery Expert for Linux, UNIX and Windows version 5.5 Interim Fix 002 contains an HTTP header injection vulnerability caused by improper validation of input through HOST headers. This flaw could allow an attacker to conduct various attacks against the vulnerable system, including cross-site scripting, cache poisoning, or session hijacking.
Critical Impact
Attackers can manipulate HTTP HOST headers to inject malicious content, potentially leading to cross-site scripting attacks, cache poisoning, or session hijacking against users of the IBM DB2 Recovery Expert application.
Affected Products
- IBM Db2 Recovery Expert for Linux, UNIX and Windows 5.5 Interim Fix 002
Discovery Timeline
- 2026-02-17 - CVE-2025-27901 published to NVD
- 2026-02-18 - Last updated in NVD database
Technical Details for CVE-2025-27901
Vulnerability Analysis
This vulnerability is classified under CWE-644: Improper Neutralization of HTTP Headers for Scripting Syntax. The IBM Db2 Recovery Expert application fails to properly validate and sanitize HTTP HOST header values before processing them. When user-controlled data from the HOST header is reflected in HTTP responses or used in application logic without adequate validation, it creates opportunities for header injection attacks.
The network-accessible nature of this vulnerability means that remote attackers can exploit it without authentication. The impact primarily affects the confidentiality and integrity of user sessions and cached content, though availability is not directly impacted.
Root Cause
The root cause lies in the improper validation of input received through HTTP HOST headers. The application accepts HOST header values without sufficient sanitization, allowing attackers to inject arbitrary header content or manipulate how the application generates URLs and redirects. This is a common weakness pattern where web applications trust client-provided headers that can be easily manipulated by attackers.
Attack Vector
An attacker can exploit this vulnerability by sending crafted HTTP requests with malicious HOST header values to the IBM Db2 Recovery Expert web interface. The attack vector is network-based, requiring no authentication or user privileges.
The exploitation mechanism involves crafting HTTP requests where the HOST header contains injected content such as CRLF sequences (carriage return/line feed) followed by additional headers or script content. When the vulnerable application incorporates this unsanitized header value into responses, it enables several attack scenarios:
- Cross-Site Scripting (XSS): Injected script content may be executed in the context of legitimate users' browsers
- Cache Poisoning: Malicious responses can be cached by intermediary proxies, affecting subsequent users
- Session Hijacking: Attackers can manipulate session-related headers to intercept or fixate user sessions
For detailed technical information, refer to the IBM Support Page.
Detection Methods for CVE-2025-27901
Indicators of Compromise
- Unusual or malformed HOST header values in web server access logs containing CRLF sequences or encoded characters
- HTTP responses containing unexpected headers or script content injected via header manipulation
- Evidence of cache entries with manipulated content that differ from legitimate application responses
- Session anomalies indicating potential hijacking attempts, such as session tokens appearing in unexpected contexts
Detection Strategies
- Implement web application firewall (WAF) rules to detect and block requests with CRLF injection patterns in HTTP headers
- Configure intrusion detection systems (IDS) to alert on HTTP requests containing suspicious HOST header patterns
- Review web server logs for HOST headers containing special characters, encoded values, or unexpected domain names
- Deploy SentinelOne Singularity XDR to monitor for exploitation attempts and anomalous HTTP traffic patterns
Monitoring Recommendations
- Enable detailed HTTP header logging on web servers hosting IBM Db2 Recovery Expert
- Monitor for unusual patterns in cached content that may indicate cache poisoning attempts
- Implement real-time alerting for requests with HOST headers that deviate from expected domain values
- Track session creation patterns and flag sessions with anomalous characteristics
How to Mitigate CVE-2025-27901
Immediate Actions Required
- Apply the latest security update from IBM as referenced in the IBM Support Page
- Implement strict HOST header validation at the web application firewall or reverse proxy level
- Configure web servers to reject requests with HOST headers that do not match expected domain values
- Review and audit existing application configurations for proper input validation settings
Patch Information
IBM has acknowledged this vulnerability and provides remediation guidance through their official support channels. Administrators should consult the IBM Support Page for the latest patch information and apply the recommended security update for IBM Db2 Recovery Expert for Linux, UNIX and Windows version 5.5.
Workarounds
- Configure a reverse proxy or load balancer to normalize and validate HOST headers before forwarding requests to the application
- Implement allowlist-based validation for acceptable HOST header values at the network perimeter
- Deploy web application firewall rules to strip or reject requests with suspicious header content including CRLF sequences
- Restrict network access to the IBM Db2 Recovery Expert web interface to trusted administrative networks only
# Example Apache configuration to validate HOST headers
# Add to virtual host configuration
RewriteEngine On
RewriteCond %{HTTP_HOST} !^(expected-hostname\.example\.com)$ [NC]
RewriteRule ^ - [F,L]
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
