CVE-2001-0327 in Web Server
Summary
by MITRE
iPlanet Web Server Enterprise Edition 4.1 and earlier allows remote attackers to retrieve sensitive data from memory allocation pools, or cause a denial of service, via a URL-encoded Host: header in the HTTP request, which reveals memory in the Location: header that is returned by the server.
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Analysis
by VulDB Data Team • 10/07/2025
The vulnerability described in CVE-2001-0327 affects the iPlanet Web Server Enterprise Edition version 4.1 and earlier, representing a critical security flaw that exposes sensitive information through improper handling of HTTP request headers. This issue stems from the server's inadequate processing of URL-encoded Host: headers in HTTP requests, which creates a memory disclosure vulnerability that can be exploited by remote attackers to gain access to confidential data stored in memory allocation pools. The flaw specifically manifests when the server processes malformed Host headers and subsequently includes memory contents in the Location: response header, effectively leaking sensitive information from the server's memory space.
The technical implementation of this vulnerability involves the server's failure to properly validate or sanitize the Host: header parameter before incorporating it into the response. When an attacker submits a specially crafted URL-encoded Host: header, the web server processes this input without adequate boundary checking or memory management, resulting in the inclusion of arbitrary memory contents within the Location: header of the HTTP response. This memory disclosure occurs because the server's internal memory allocation structures contain remnants of previous operations, including potentially sensitive data such as session tokens, database credentials, or other confidential information that was previously stored in the same memory regions. The vulnerability operates at the application layer and demonstrates poor input validation practices that violate fundamental security principles outlined in CWE-20, which addresses improper input validation.
The operational impact of this vulnerability extends beyond simple information disclosure to include potential denial of service conditions and increased attack surface for more sophisticated exploitation attempts. Remote attackers can leverage this vulnerability to gather intelligence about the server environment, potentially identifying system configurations, application versions, or other sensitive information that could be used in subsequent attacks. The memory leakage could expose session identifiers, cryptographic keys, or other critical data that would otherwise remain protected within the server's memory space. This type of vulnerability aligns with ATT&CK technique T1552.001, which covers "Unsecured Credentials" through memory dumps, and represents a classic example of how improper handling of user input can lead to information exposure. The vulnerability also demonstrates characteristics of privilege escalation and information gathering that could enable attackers to move laterally within a network or target other systems that share similar credentials or configurations.
Mitigation strategies for CVE-2001-0327 should focus on immediate patching of the iPlanet Web Server to version 4.1 or later, where the vulnerability has been addressed through proper input validation and memory management practices. Organizations should implement strict header validation mechanisms that sanitize all incoming Host: header parameters before processing, ensuring that URL-encoded values are properly decoded and validated against expected formats. Network segmentation and access controls can help limit the impact of successful exploitation by reducing the potential attack surface. Additionally, monitoring systems should be configured to detect unusual patterns in Location: headers that might indicate memory disclosure attempts. The vulnerability highlights the importance of following secure coding practices and adhering to security standards such as those defined in the OWASP Top Ten, particularly focusing on input validation and output encoding to prevent similar issues in web applications. Regular security assessments and penetration testing should be conducted to identify and remediate similar vulnerabilities in web server configurations and application code.