CVE-2000-1208 in NetBSD
Summary
by MITRE
Format string vulnerability in startprinting() function of printjob.c in BSD-based lpr lpd package may allow local users to gain privileges via an improper syslog call that uses format strings from the checkremote() call.
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Analysis
by VulDB Data Team • 05/09/2019
The vulnerability described in CVE-2000-1208 represents a critical format string flaw within the BSD-based lpr lpd printing package that affects local users with the potential to escalate privileges. This issue resides in the startprinting() function of the printjob.c file and demonstrates how improper handling of user-supplied data can lead to significant security implications. The vulnerability specifically manifests through an unsafe syslog() call that incorporates format specifiers directly from the checkremote() function without proper sanitization or validation.
The technical execution of this vulnerability occurs when the lpr lpd service processes print jobs and calls the checkremote() function to validate remote printing requests. The output from this validation process contains format string specifiers that are then directly passed to the syslog() function within startprinting(). This improper handling creates a classic format string vulnerability where malicious input can contain format specifiers such as %x, %s, or %n that, when processed by the syslog function, can result in memory disclosure, arbitrary code execution, or privilege escalation. The vulnerability is particularly dangerous because it operates within a privileged context where the lpr daemon typically runs with elevated permissions.
The operational impact of CVE-2000-1208 extends beyond simple privilege escalation to potentially enable full system compromise. Local attackers who can submit print jobs to the lpd service can exploit this vulnerability to execute arbitrary code with the privileges of the printing daemon, which often runs as root or with administrative privileges. This allows attackers to read sensitive memory locations, overwrite critical memory areas, or even execute shellcode directly within the context of the privileged process. The vulnerability's local nature means that attackers do not require network access or remote exploitation capabilities, making it particularly concerning for systems where local access is possible.
The root cause of this vulnerability aligns with CWE-134, which specifically addresses the use of format strings in system calls without proper validation or sanitization. This weakness creates a direct pathway for attackers to manipulate the execution flow of the application through carefully crafted input that contains format specifiers. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the use of insecure system calls and improper input handling within privileged processes. Organizations should consider implementing strict input validation, using safe string formatting functions such as snprintf() instead of sprintf(), and ensuring that all user-supplied data passed to system calls undergoes proper sanitization before processing.
Mitigation strategies for this vulnerability include immediate patching of affected systems with updated lpr lpd packages from respective vendors, implementing input validation mechanisms that reject format specifiers in user-supplied data, and restricting local access to printing services where possible. System administrators should also consider implementing additional monitoring for suspicious syslog entries and ensure that the lpd service runs with minimal required privileges. The vulnerability highlights the importance of secure coding practices and proper input sanitization in privileged system components, particularly when dealing with logging and system call operations that may be exposed to untrusted input sources.