CVE-2001-1215 in PFinger
Summary
by MITRE
Format string vulnerability in PFinger 0.7.5 through 0.7.7 allows remote attackers to execute arbitrary code via format string specifiers in a .plan file.
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Analysis
by VulDB Data Team • 05/24/2019
The vulnerability identified as CVE-2001-1215 represents a critical format string flaw in PFinger versions 0.7.5 through 0.7.7 that enables remote code execution through maliciously crafted input in .plan files. This vulnerability resides in the finger protocol implementation that serves user information from remote systems, making it a significant concern for network security infrastructure. The flaw stems from improper input validation where the application directly incorporates user-supplied data into format string functions without adequate sanitization or encoding. The .plan file mechanism, commonly used by finger services to display user information, becomes a vector for exploitation when attackers craft malicious format specifiers that can manipulate the program's execution flow.
The technical exploitation of this vulnerability occurs when a remote attacker places specially formatted strings containing format specifiers such as %x, %s, or %n within a .plan file hosted on a vulnerable PFinger server. These format specifiers can cause the application to read or write data from memory locations, potentially leading to stack corruption, information disclosure, or arbitrary code execution. The vulnerability specifically targets the printf family of functions that are commonly used for string formatting operations, and when these functions receive untrusted input directly, they can be manipulated to execute unintended operations. This type of vulnerability maps directly to CWE-134, which defines the weakness of using user-supplied format strings in functions like printf, and aligns with ATT&CK technique T1059.007 for command and script injection.
The operational impact of CVE-2001-1215 extends beyond simple privilege escalation as it provides attackers with a pathway to gain full control over affected systems running vulnerable PFinger versions. Network administrators and security professionals must recognize that finger services, while seemingly obsolete, still remain active in many environments and continue to pose security risks. The vulnerability's remote exploitability means that attackers do not require local access to compromise systems, making it particularly dangerous in networked environments where finger services are exposed to the internet. This type of vulnerability also demonstrates the importance of proper input validation and the principle of least privilege, as the attack can potentially escalate to root privileges if the finger service runs with elevated permissions. Organizations should consider the broader implications of legacy services and their continued operation in modern security environments.
Mitigation strategies for CVE-2001-1215 should prioritize immediate patching of affected PFinger installations to versions that properly sanitize user input before processing. System administrators should disable finger services entirely when not required, as these services often represent unnecessary attack vectors in modern network architectures. Network segmentation and firewall rules can help limit exposure by blocking access to finger service ports, typically port 79. Additionally, implementing proper input validation mechanisms that reject format specifiers in user-supplied content can prevent exploitation attempts. Security monitoring should include detection of unusual .plan file content and monitoring for potential exploitation attempts. Organizations should also consider implementing intrusion detection systems that can identify patterns associated with format string exploitation attempts. The vulnerability underscores the critical importance of regular security assessments and vulnerability management programs that can identify and remediate legacy service risks before they can be exploited by malicious actors.