CVE-2009-1601 in Linux
Summary
by MITRE
The Ubuntu clamav-milter.init script in clamav-milter before 0.95.1+dfsg-1ubuntu1.2 in Ubuntu 9.04 sets the ownership of the current working directory to the clamav account, which might allow local users to bypass intended access restrictions via read or write operations involving this directory.
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Analysis
by VulDB Data Team • 09/04/2019
The vulnerability described in CVE-2009-1601 represents a significant privilege escalation risk within the Ubuntu clamav-milter package ecosystem. This issue affects versions of clamav-milter prior to 0.95.1+dfsg-1ubuntu1.2 in Ubuntu 9.04, where the initialization script contains a critical flaw that undermines the security posture of the mail filtering service. The vulnerability stems from improper handling of file system permissions during the service startup process, creating an attack vector that local malicious users can exploit to gain elevated privileges.
The technical flaw manifests in the clamav-milter.init script which, during execution, explicitly sets the ownership of the current working directory to the clamav user account. This behavior is particularly dangerous because it allows any local user who can influence the working directory to potentially manipulate file permissions and access controls. When the script executes with elevated privileges during system startup or service initialization, it inadvertently grants the clamav user account ownership of whatever directory happens to be the current working directory at execution time. This creates a scenario where a local attacker can craft a malicious working directory structure that, when accessed by the initialization script, results in unintended privilege escalation.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it represents a fundamental flaw in the principle of least privilege implementation within the mail filtering infrastructure. The attack surface is particularly concerning because the clamav-milter service typically runs with elevated privileges to properly scan and filter mail content, making the potential for abuse more significant. Local users who can control or influence the working directory during script execution can potentially read or write files that should normally be restricted to the clamav user account. This could enable attackers to modify configuration files, inject malicious code, or access sensitive data that the service is designed to protect. The vulnerability also aligns with CWE-276, which addresses improper file permissions and inadequate access control mechanisms.
From an attacker's perspective, this vulnerability provides a straightforward path to privilege escalation that requires minimal specialized knowledge or resources. The attack vector is particularly effective because it exploits the legitimate administrative functionality of the initialization script while introducing unintended security implications. The ATT&CK framework categorizes this as a privilege escalation technique under the 'Abuse Elevation of Privilege' tactic, where attackers leverage legitimate system functionality to gain unauthorized access. The vulnerability is especially problematic in multi-user environments where local users might have access to the system but should not have the ability to manipulate service configurations or access restricted files. The long-term implications include potential data exfiltration, service disruption, and further escalation opportunities that could compromise the entire mail filtering infrastructure.
The recommended mitigation strategy involves updating to the patched version of clamav-milter (0.95.1+dfsg-1ubuntu1.2 or later) which properly handles directory ownership and permissions. System administrators should also implement additional monitoring of the initialization script execution and directory access patterns to detect potential exploitation attempts. The fix typically involves ensuring that the script does not set ownership of arbitrary directories and instead uses explicit, secure directory paths that are properly configured with appropriate permissions. Organizations should conduct thorough security audits of their mail filtering infrastructure to identify any similar privilege escalation vulnerabilities and ensure that all service initialization processes follow secure coding practices that prevent unintended access control modifications.