CVE-2008-6520 in Xitami
Summary
by MITRE
Multiple format string vulnerabilities in the SSI filter in Xitami Web Server 2.5c2, and possibly other versions, allow remote attackers to cause a denial of service (daemon crash) and possibly execute arbitrary code via format string specifiers in a URI that ends in (1) .ssi, (2) .shtm, or (3) .shtml, which triggers incorrect logging code involving the sendfmt function in the SMT kernel.
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Analysis
by VulDB Data Team • 11/03/2018
The CVE-2008-6520 vulnerability represents a critical format string vulnerability within the SSI filter of Xitami Web Server version 2.5c2 and potentially other iterations. This flaw exists in the server's handling of server-side includes and specifically affects files with extensions .ssi, .shtm, and .shtml. The vulnerability stems from improper input validation and handling within the sendfmt function located in the SMT kernel, which processes logging operations for these specific file types.
The technical exploitation of this vulnerability occurs when remote attackers craft malicious URIs containing format string specifiers that end with the targeted file extensions. When the web server processes these requests, the malformed format strings cause the sendfmt function to behave unpredictably during logging operations. This improper handling of format specifiers can lead to stack corruption, memory access violations, and ultimately daemon crashes that result in denial of service conditions. The vulnerability's potential for arbitrary code execution arises from the ability of attackers to manipulate the format string parameters to overwrite critical memory locations or redirect program execution flow.
From an operational impact perspective, this vulnerability creates significant security risks for organizations relying on Xitami Web Server 2.5c2. The denial of service component can render web services unavailable to legitimate users, while the potential for arbitrary code execution could allow attackers to gain full control over the affected server. The vulnerability affects the core web server functionality since it operates at the kernel level within the SMT subsystem, making it particularly dangerous as it can compromise the entire server infrastructure. Network administrators face the challenge of identifying and mitigating this issue without disrupting legitimate web content delivery.
The vulnerability aligns with CWE-134, which specifically addresses format string vulnerabilities where format strings are constructed from user-supplied data without proper validation. This weakness creates a direct pathway for attackers to manipulate program execution through carefully crafted input sequences. From an ATT&CK framework perspective, this vulnerability maps to initial access and execution techniques, as attackers can leverage it to establish persistent access to target systems. The exploit requires minimal network interaction and can be automated, making it particularly attractive for exploitation at scale.
Mitigation strategies for CVE-2008-6520 should prioritize immediate patching of affected Xitami Web Server installations to version 2.5c3 or later, which contains the necessary fixes for the format string handling issues. Organizations should also implement network-level restrictions to limit access to .ssi, .shtm, and .shtml file extensions where possible, and deploy intrusion detection systems that can identify suspicious format string patterns in web traffic. Additional protective measures include disabling SSI functionality if not essential, implementing proper input validation for all URI parameters, and conducting regular security assessments of web server configurations to identify similar vulnerabilities. The vulnerability demonstrates the importance of proper input sanitization and the critical need for regular security updates in web server implementations.