CVE-2001-0748 in Acme.Serve
Summary
by MITRE
Acme.Serve 1.7, as used in Cisco Secure ACS Unix and possibly other products, allows remote attackers to read arbitrary files by prepending several / (slash) characters to the URI.
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Analysis
by VulDB Data Team • 10/04/2025
The vulnerability identified as CVE-2001-0748 represents a classic path traversal flaw in the Acme.Serve web server component version 1.7 that was integrated into Cisco Secure ACS Unix and potentially other affected products. This issue stems from inadequate input validation within the web server's URI processing mechanism, allowing malicious actors to exploit the system's file access controls through carefully crafted requests. The vulnerability specifically manifests when attackers prepend multiple forward slash characters to the requested URI, effectively bypassing normal file system access restrictions and enabling arbitrary file reading capabilities.
The technical exploitation of this vulnerability leverages the web server's failure to properly sanitize or normalize URI paths before processing file requests. When a user submits a request containing multiple consecutive slash characters at the beginning of the URI, the web server interprets these sequences incorrectly, allowing the attacker to traverse the file system hierarchy and access files that should normally be restricted. This behavior directly violates the principle of least privilege and demonstrates a fundamental flaw in the application's security architecture. The vulnerability is classified under CWE-22 as "Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')" which is one of the most commonly exploited categories of web application vulnerabilities. The flaw essentially allows an attacker to craft requests that can access sensitive system files, configuration data, or other restricted resources that should not be accessible through normal web browsing operations.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the capability to access critical system files that may contain sensitive data, authentication credentials, or system configuration details. In the context of Cisco Secure ACS Unix, this vulnerability could potentially expose authentication databases, configuration files containing administrative passwords, or other sensitive operational data that would normally be protected by proper file system permissions. The remote nature of the attack means that an attacker does not require physical access to the system or local network privileges to exploit this vulnerability, making it particularly dangerous in networked environments where the web server is exposed to untrusted users. This vulnerability aligns with ATT&CK technique T1083 (File and Directory Discovery) and T1566 (Phishing) as attackers could use this weakness to gather intelligence about the target system and potentially escalate privileges through the information obtained.
Mitigation strategies for CVE-2001-0748 should focus on implementing proper input validation and normalization of URI paths before file access operations are performed. Organizations should immediately update to patched versions of Acme.Serve or Cisco Secure ACS Unix that address this path traversal vulnerability. The implementation of web application firewalls or security proxies that can detect and block suspicious URI patterns containing multiple consecutive slash characters provides an additional layer of protection. System administrators should also implement proper file system access controls and ensure that the web server process runs with minimal required privileges, following the principle of least privilege. Regular security assessments and penetration testing should be conducted to identify similar path traversal vulnerabilities in other web applications and services. Additionally, organizations should consider implementing proper logging and monitoring of file access patterns to detect potential exploitation attempts, as this vulnerability could be used as part of a broader attack chain leading to more severe compromises of the affected systems.