CVE-2005-3258 in IPCop
Summary
by MITRE
The rfc1738_do_escape function in ftp.c for Squid 2.5 STABLE11 and earlier allows remote FTP servers to cause a denial of service (segmentation fault) via certain "odd" responses.
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Analysis
by VulDB Data Team • 09/05/2019
The vulnerability identified as CVE-2005-3258 represents a critical denial of service flaw within the Squid proxy server software, specifically affecting versions 2.5 STABLE11 and earlier. This issue stems from improper handling of FTP server responses during the URL parsing process, where the rfc1738_do_escape function fails to adequately validate or sanitize input from remote FTP servers. The flaw manifests when the function encounters certain "odd" or malformed responses from FTP servers, causing the proxy to crash with a segmentation fault that results in complete service disruption. This vulnerability operates at the application layer and demonstrates a classic buffer over-read or improper input validation issue that can be exploited by malicious FTP servers to compromise the availability of the proxy service.
The technical implementation of this vulnerability resides in the ftp.c source file where the rfc1738_do_escape function processes FTP URL escape sequences. When a remote FTP server returns responses containing unexpected character sequences or malformed data structures, the function does not properly check bounds or validate the input before processing. This lack of input validation creates a scenario where memory access violations occur, leading to segmentation faults that terminate the Squid process. The vulnerability is particularly concerning because it allows remote attackers to trigger this condition without requiring authentication or special privileges, making it an attractive target for denial of service attacks against proxy infrastructure. The flaw aligns with CWE-121, which describes stack-based buffer overflow conditions, and demonstrates how improper input validation can lead to memory corruption vulnerabilities.
From an operational perspective, this vulnerability presents significant risk to organizations relying on Squid as their primary proxy server solution, particularly those with high availability requirements or those serving critical network functions. The segmentation fault caused by this vulnerability results in immediate service disruption, forcing administrators to manually restart the proxy service and potentially causing temporary loss of network connectivity for all users dependent on that proxy. The impact extends beyond simple service interruption as it can affect business continuity, especially in environments where proxy servers are critical components of network infrastructure. Attackers can exploit this vulnerability by simply connecting to a malicious FTP server that returns the specific malformed responses, making the attack surface extremely broad and easy to execute. This vulnerability also maps to ATT&CK technique T1499.004, which covers "Toggle Service," as the exploitation results in service disruption through controlled crashes.
The mitigation strategies for this vulnerability involve immediate patching of Squid installations to versions 2.5 STABLE12 or later, where the input validation issues have been addressed. Organizations should also implement network segmentation and firewall rules to limit exposure to untrusted FTP servers, particularly in environments where the proxy handles sensitive traffic. Additional defensive measures include implementing intrusion detection systems to monitor for unusual FTP response patterns and configuring proxy servers with proper logging and alerting mechanisms to detect potential exploitation attempts. Network administrators should also consider implementing rate limiting and connection monitoring to prevent rapid exploitation attempts that could overwhelm the system. The fix implemented in later versions of Squid typically involves enhanced input validation routines and proper bounds checking within the rfc1738_do_escape function to prevent memory access violations when processing malformed FTP responses. Organizations should conduct thorough testing of updated software in staging environments before deployment to ensure compatibility with existing network configurations and avoid unintended service disruptions.