CVE-1999-0340 in Linux
Summary
by MITRE
buffer overflow in linux slackware crond program allows local users to gain root access.
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Analysis
by VulDB Data Team • 04/17/2026
The vulnerability described in CVE-1999-0340 represents a critical buffer overflow flaw within the crond program of Slackware Linux systems, specifically targeting the cron daemon responsible for executing scheduled tasks. This issue arises from improper input validation within the cron service implementation, creating a pathway for local attackers to escalate privileges to root level access. The flaw exists in the handling of command line arguments passed to the cron daemon, where insufficient bounds checking allows attackers to overwrite memory segments beyond the allocated buffer space. The vulnerability operates at the system level, leveraging the inherent trust placed in the cron service to execute scheduled tasks with elevated privileges, making it particularly dangerous in multi-user environments where local users might attempt to exploit this weakness.
The technical exploitation of this buffer overflow occurs when a local user crafts malicious input that exceeds the predetermined buffer size within the crond program's memory allocation. This overflow corrupts adjacent memory locations, potentially overwriting critical program variables, return addresses, or function pointers that control the execution flow. The vulnerability manifests as a classic stack-based buffer overflow scenario, where the attacker can manipulate the program's execution path by overwriting the return address on the stack, effectively redirecting control flow to malicious code. The flaw is particularly concerning because it allows privilege escalation without requiring network access or external attack vectors, making it an attractive target for local attackers who already have system access. According to CWE classification, this represents a CWE-121 stack-based buffer overflow vulnerability that directly enables unauthorized privilege escalation.
The operational impact of CVE-1999-0340 extends beyond simple local privilege escalation, as it fundamentally compromises the integrity of the system's security model. When exploited successfully, the vulnerability allows attackers to execute arbitrary code with root privileges, potentially leading to complete system compromise, data exfiltration, or persistent backdoor installation. The attack vector is particularly dangerous in shared hosting environments, multi-user systems, or any scenario where local users might have access to the system but lack administrative privileges. The vulnerability's exploitation can occur silently without generating obvious audit trails, making detection challenging for system administrators. Organizations using affected Slackware versions face significant risk of unauthorized access and potential data breaches, as the flaw enables attackers to bypass traditional access controls and gain unrestricted system access. This vulnerability directly aligns with ATT&CK technique T1068 which covers local privilege escalation through exploitation of system-level vulnerabilities.
Mitigation strategies for this vulnerability require immediate patching of the affected crond implementation with proper buffer size validation and bounds checking. System administrators should ensure that all Slackware systems are updated to versions containing fixes for this buffer overflow, as the vulnerability represents an unpatched security flaw that has been widely known since 1999. Additional protective measures include implementing proper access controls to limit local user privileges, monitoring cron job execution through audit logs, and employing intrusion detection systems to identify potential exploitation attempts. The fix should incorporate proper input validation techniques such as using safe string handling functions, implementing stack canaries, and employing address space layout randomization to make exploitation more difficult. Organizations should also conduct regular security assessments to identify similar vulnerabilities in other system components, as this flaw demonstrates the importance of secure coding practices in system-level services. The vulnerability serves as a reminder of the critical need for regular security updates and proper code review processes to prevent such fundamental flaws from persisting in production systems.