CVE-2001-0609 in cfingerd
Summary
by MITRE
Format string vulnerability in Infodrom cfingerd 1.4.3 and earlier allows a remote attacker to gain additional privileges via a malformed ident reply that is passed to the syslog function.
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Analysis
by VulDB Data Team • 10/05/2025
The vulnerability identified as CVE-2001-0609 represents a critical format string flaw within the Infodrom cfingerd version 1.4.3 and earlier implementations. This vulnerability specifically manifests when the service processes malformed ident replies that are subsequently passed to the syslog function, creating a pathway for remote attackers to exploit the system's privilege escalation mechanisms. The flaw resides in the improper handling of user-supplied input data that gets directly incorporated into format string operations without adequate sanitization or validation measures.
This type of vulnerability falls under the CWE-134 category known as "Use of Externally-Controlled Format String," which is classified as a high-severity weakness in software security practices. The attack vector leverages the inherent trust placed in ident protocol responses, where cfingerd accepts and processes ident replies without sufficient input validation. When a malicious attacker crafts a specially formatted ident reply containing format specifiers such as %n, %x, or %s, these sequences can be interpreted by the syslog function as instructions for memory access or output formatting rather than literal text, potentially leading to arbitrary code execution or privilege escalation.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it enables remote attackers to gain elevated privileges on the affected system. The syslog function serves as a critical logging mechanism within Unix-like systems, and when manipulated through format string exploitation, attackers can potentially overwrite system memory locations or redirect execution flow. This vulnerability directly aligns with ATT&CK technique T1068 which describes "Exploitation for Privilege Escalation" and demonstrates how seemingly benign network protocols can become attack vectors for system compromise. The vulnerability affects systems where cfingerd operates as a privileged service, typically running with elevated permissions to perform network operations and access system resources.
Mitigation strategies for CVE-2001-0609 require immediate patching of the cfingerd service to version 1.4.4 or later, which contains the necessary fixes to properly validate and sanitize ident reply inputs. Organizations should implement network segmentation to limit access to cfingerd services and disable the service entirely if it is not essential for operations. Additionally, implementing proper input validation mechanisms that filter out format specifiers from user-supplied data before processing, combined with regular security auditing of network services, will significantly reduce the attack surface. The vulnerability also highlights the importance of following secure coding practices such as using safe string formatting functions like snprintf instead of sprintf, and avoiding direct incorporation of external data into format strings. System administrators should also consider implementing intrusion detection systems that monitor for suspicious ident protocol traffic patterns and maintain up-to-date vulnerability management processes to prevent similar issues from occurring in other network services.