CVE-2006-2607 in cron
Summary
by MITRE
do_command.c in Vixie cron (vixie-cron) 4.1 does not check the return code of a setuid call, which might allow local users to gain root privileges if setuid fails in cases such as PAM failures or resource limits, as originally demonstrated by a program that exceeds the process limits as defined in /etc/security/limits.conf.
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Analysis
by VulDB Data Team • 06/21/2025
The vulnerability described in CVE-2006-2607 resides within the vixie-cron package version 4.1 where the do_command.c component fails to properly validate the return code of setuid system calls. This critical flaw represents a privilege escalation vulnerability that directly impacts the security model of the cron daemon. The issue occurs when the cron service attempts to elevate privileges using setuid mechanisms but does not verify whether these operations succeed or fail. When setuid calls fail due to various conditions such as PAM authentication failures or resource limitation constraints defined in /etc/security/limits.conf, the system continues execution without proper privilege validation, creating an exploitable condition. This vulnerability is particularly dangerous because it operates within a core system service that typically runs with elevated privileges, making it an attractive target for local attackers seeking to escalate their privileges to root access.
The technical implementation of this vulnerability stems from poor error handling practices within the setuid call sequence. In Unix-like systems, the setuid mechanism is designed to temporarily elevate process privileges to execute commands with the permissions of the file owner rather than the user who invoked the process. When vixie-cron performs a setuid operation to execute scheduled tasks, it must validate that this privilege escalation was successful before proceeding. However, the flaw in do_command.c means that even if the setuid call fails due to system limitations or authentication failures, the program continues execution with the original user privileges instead of properly handling the failure condition. This creates a scenario where an attacker can manipulate system resources or authentication mechanisms to cause the setuid call to fail, thereby allowing the program to continue running with reduced privileges while potentially bypassing security checks that would normally prevent privilege escalation.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass broader system compromise potential. When local users can exploit this condition, they gain the ability to execute commands with root privileges, effectively compromising the entire system. The vulnerability is particularly concerning because it can be triggered by resource exhaustion scenarios that are common in system environments, such as exceeding process limits defined in /etc/security/limits.conf. Attackers can leverage this by creating programs that consume system resources to force setuid calls to fail, thereby enabling privilege escalation. This vulnerability aligns with CWE-252, which describes "Unchecked Return Value" conditions that can lead to security flaws, and represents a classic example of how improper error handling can create security vulnerabilities in system-level software. The attack vector is primarily local, meaning any user with access to the system can potentially exploit this weakness, making it particularly dangerous in multi-user environments.
Mitigation strategies for this vulnerability require immediate system updates and careful configuration management. The primary remediation involves upgrading to a patched version of vixie-cron where proper error checking has been implemented for setuid calls. System administrators should also review and tighten resource limits in /etc/security/limits.conf to prevent resource exhaustion attacks that could trigger the vulnerability. Additionally, monitoring should be implemented to detect unusual patterns of setuid failures or privilege escalation attempts. Security hardening practices such as implementing mandatory access controls and privilege separation can further reduce the impact of such vulnerabilities. The ATT&CK framework categorizes this issue under privilege escalation techniques where adversaries leverage software vulnerabilities to gain elevated privileges, specifically targeting the 'Setuid' and 'Exploitation for Privilege Escalation' tactics. Organizations should also implement regular vulnerability assessments and maintain updated security patches to prevent exploitation of similar issues in other system components that may exhibit similar error handling flaws.