CVE-2001-0735 in cfingerd
Summary
by MITRE
Buffer overflow in cfingerd 1.4.3 and earlier with the ALLOW_LINE_PARSING option enabled allows local users to execute arbitrary code via a long line in the .nofinger file.
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Analysis
by VulDB Data Team • 10/04/2025
The vulnerability identified as CVE-2001-0735 represents a critical buffer overflow flaw within the cfingerd daemon version 1.4.3 and earlier implementations. This issue specifically manifests when the ALLOW_LINE_PARSING option is enabled, creating a dangerous condition where local users can manipulate the .nofinger file to trigger memory corruption. The cfingerd service operates as a finger protocol daemon that traditionally provides user information services over network connections, making it a potential target for privilege escalation attacks within systems where this service is actively running.
The technical exploitation of this vulnerability stems from improper input validation within the line parsing functionality of cfingerd. When the daemon processes lines within the .nofinger file, it fails to properly bounds-check the input data against the allocated buffer space. This allows an attacker to provide a line that exceeds the predetermined buffer limits, causing adjacent memory locations to be overwritten with attacker-controlled data. The buffer overflow occurs during the parsing phase of the .nofinger file processing, where the daemon's internal string handling routines do not validate the length of input lines before copying them into fixed-size buffers.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it enables local privilege escalation attacks that can result in arbitrary code execution with the privileges of the cfingerd process. Since the daemon typically runs with elevated privileges to access user information files, successful exploitation could allow attackers to gain root access or at minimum escalate their privileges to the level of the service account. This presents a significant risk in environments where cfingerd is installed and running with administrative privileges, particularly in older Unix-like systems where security hardening practices were less prevalent.
This vulnerability maps directly to CWE-121, which describes stack-based buffer overflow conditions, and also relates to CWE-787, describing out-of-bounds write conditions. From an ATT&CK framework perspective, this represents a privilege escalation technique through local exploitation, specifically categorized under T1068, which involves exploiting vulnerabilities in local services. The attack vector requires local access to the system and involves manipulating configuration files to trigger the buffer overflow condition, making it a low-impact but high-consequence vulnerability that could be exploited by users with minimal system access.
Mitigation strategies for CVE-2001-0735 should prioritize immediate patching of affected cfingerd installations to versions that address the buffer overflow conditions in line parsing. Organizations should disable the ALLOW_LINE_PARSING option if it is not strictly required for service functionality, as this removes the attack surface entirely. Additionally, system administrators should implement proper file access controls on the .nofinger file and related configuration directories to limit local user modification capabilities. Regular security audits should verify that no outdated versions of cfingerd remain installed on systems, and network segmentation should prevent unnecessary exposure of finger protocol services to external networks. The vulnerability also underscores the importance of input validation and bounds checking in legacy network services, particularly those that handle user-provided data without adequate sanitization measures.