CVE-2008-0694 in OS400
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the HTTP Server in IBM OS/400 V5R3M0 and V5R4M0 allows remote attackers to inject arbitrary web script or HTML via the Expect HTTP header.
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Analysis
by VulDB Data Team • 11/10/2017
The vulnerability identified as CVE-2008-0694 represents a critical cross-site scripting flaw within the HTTP Server component of IBM OS/400 operating system versions V5R3M0 and V5R4M0. This vulnerability resides in the server's handling of HTTP headers, specifically the Expect header field, which creates an avenue for remote attackers to execute malicious code within the context of victim browsers. The flaw stems from insufficient input validation and sanitization mechanisms that fail to properly process or escape user-supplied data before incorporating it into web responses. This particular vulnerability is classified under CWE-79 as a failure to sanitize input, making it susceptible to injection attacks that can compromise user sessions and data integrity.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious HTTP request containing a specially formatted Expect header that includes embedded script code. When the vulnerable IBM OS/400 server processes this request, it fails to adequately sanitize the Expect header content, allowing the malicious script to be executed in the browser context of any user who views the affected web page or interacts with the server response. The vulnerability affects the server's HTTP processing layer where it does not properly validate or escape input from the Expect header field, creating a persistent XSS vector that can be leveraged for session hijacking, credential theft, or redirection to malicious sites.
Operationally, this vulnerability poses significant risks to organizations utilizing IBM OS/400 systems, particularly those with web-facing applications or administrative interfaces that rely on the built-in HTTP server functionality. Attackers can exploit this flaw to steal session cookies, perform unauthorized actions on behalf of authenticated users, or redirect victims to phishing sites that can harvest sensitive information. The impact extends beyond simple script injection as it can enable complete compromise of user sessions and potentially lead to broader system infiltration. The vulnerability affects both V5R3M0 and V5R4M0 versions, indicating it was present across multiple generations of the OS/400 platform and likely affected numerous enterprise environments that had not yet upgraded to newer versions.
Organizations should implement immediate mitigations including patching the affected IBM OS/400 versions to the latest security updates provided by IBM, implementing web application firewalls to filter malicious Expect headers, and configuring input validation rules that reject or sanitize any non-standard HTTP headers. Network-level protections such as intrusion detection systems can help identify exploitation attempts, while application-level defenses should include comprehensive input sanitization and output encoding mechanisms. The vulnerability aligns with ATT&CK technique T1566 which covers social engineering attacks through malicious web content, and T1059 which encompasses command and scripting interpreters used in code injection attacks. Security teams must also consider implementing regular vulnerability assessments and penetration testing to identify similar input validation weaknesses in other server components and web applications within their environment.