CVE-2025-27901 identifies a vulnerability in IBM DB2 Recovery Expert for Linux, UNIX, and Windows (LUW) version 5.5 Interim Fix 002, where improper neutralization of HTTP headers (specifically the HOST header) leads to HTTP header injection. This vulnerability is classified under CWE-644, which involves improper neutralization of input used in HTTP headers, enabling injection of malicious scripting syntax. The flaw arises because the software fails to properly validate or sanitize the HOST header input, allowing an attacker to inject crafted HTTP headers. Exploiting this vulnerability can facilitate several attack vectors including cross-site scripting (XSS), where malicious scripts execute in the context of a trusted web application; cache poisoning, which can cause clients or proxies to cache malicious content; and session hijacking, enabling attackers to steal or manipulate user sessions. The CVSS 3.1 base score is 6.5, reflecting a medium severity with network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and impacts on confidentiality and integrity but not availability (C:L/I:L/A:N). No known exploits have been reported in the wild, but the vulnerability poses a significant risk due to its ease of exploitation and potential impact on sensitive data and session integrity. The vulnerability affects a widely used IBM database recovery tool, which is critical in enterprise environments for disaster recovery and data integrity assurance.

For European organizations, this vulnerability could lead to unauthorized disclosure of sensitive information and manipulation of session data, undermining trust and security of critical database recovery operations. Attackers exploiting this flaw could execute malicious scripts in the context of the affected application, potentially leading to credential theft, unauthorized access, or data manipulation. Cache poisoning could disrupt normal operations by serving malicious or stale content to users or systems relying on cached data. While availability is not directly impacted, the compromise of confidentiality and integrity in database recovery tools can have cascading effects on business continuity and regulatory compliance, especially under GDPR requirements. Sectors such as finance, government, healthcare, and telecommunications, which heavily rely on IBM DB2 products for data management and recovery, are particularly at risk. The medium severity rating indicates a significant but not critical threat, emphasizing the need for timely remediation to prevent exploitation.

Organizations should immediately assess their deployment of IBM DB2 Recovery Expert for LUW 5.5 Interim Fix 002 and plan to apply any forthcoming official patches from IBM as none are currently listed. In the interim, implement strict input validation and sanitization on HTTP headers at the network perimeter or within web application firewalls (WAFs) to block malformed HOST headers. Employ HTTP header security best practices such as setting Content Security Policy (CSP) headers, enabling HTTP Strict Transport Security (HSTS), and ensuring secure cookie attributes to mitigate session hijacking risks. Monitor network traffic for unusual or suspicious HTTP header patterns indicative of injection attempts. Conduct regular security assessments and penetration testing focused on HTTP header injection vectors. Additionally, restrict access to the DB2 Recovery Expert interface to trusted networks and users, and enable detailed logging and alerting to detect potential exploitation attempts early. Educate IT and security teams about this vulnerability to ensure rapid response and containment.