CVE-2004-0561 in gopherd
Summary
by MITRE
Format string vulnerability in the log routine for gopher daemon (gopherd) 3.0.3 allows remote attackers to cause a denial of service and possibly execute arbitrary code.
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Analysis
by VulDB Data Team • 05/29/2019
The vulnerability identified as CVE-2004-0561 represents a critical format string flaw within the logging functionality of the gopher daemon version 3.0.3. This issue specifically affects the gopherd service which operates as a server implementing the gopher protocol, a legacy information retrieval protocol that predates the world wide web. The vulnerability arises from improper handling of user-supplied input within the logging routines, creating a scenario where maliciously crafted input can be processed through format string functions without adequate sanitization.
The technical exploitation of this vulnerability occurs when the gopher daemon processes log messages containing format specifiers that are not properly escaped or validated. When the daemon's logging function encounters these uncontrolled format specifiers, it interprets them as instructions for formatting output rather than literal text, potentially leading to stack pointer manipulation and memory access violations. This flaw falls under the category of CWE-134, which specifically addresses the use of format strings with user-supplied data, and represents a classic example of a format string vulnerability that can be leveraged for both denial of service and arbitrary code execution attacks.
From an operational perspective, this vulnerability presents significant risk to systems running the affected gopher daemon version, as remote attackers can exploit it without authentication requirements. The impact extends beyond simple service disruption to potentially allow full system compromise, making it particularly dangerous in environments where gopher services are exposed to untrusted networks. The gopher protocol, while largely obsolete, continues to be supported on many systems for backward compatibility, creating an unexpected attack surface that security administrators may overlook.
The exploitation of this vulnerability typically follows a pattern where attackers craft specially formatted input that includes format specifiers such as %x, %s, or %n, which when processed by the vulnerable logging function can cause memory corruption, stack smashing, or direct code execution. The attacker can leverage this to overwrite critical memory locations, redirect program execution flow, or cause the daemon to crash and restart, thereby achieving denial of service. This vulnerability demonstrates the critical importance of input validation in server applications and aligns with ATT&CK technique T1211 which covers the exploitation of format string vulnerabilities to gain arbitrary code execution.
Mitigation strategies for CVE-2004-0561 should prioritize immediate patching of the gopher daemon to a version that properly validates and sanitizes all user input before processing it through logging functions. Organizations should implement network segmentation to limit access to gopher services and consider disabling the gopher daemon entirely if it is not required for business operations. Additionally, deploying intrusion detection systems that monitor for suspicious format string patterns and implementing proper input validation controls can provide defense-in-depth measures. The vulnerability serves as a reminder of the persistent risks associated with legacy protocols and the necessity of maintaining up-to-date security practices even for outdated services that may still be present in production environments.