CVE-1999-0475 in Procmail
Summary
by MITRE
A race condition in how procmail handles .procmailrc files allows a local user to read arbitrary files available to the user who is running procmail.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-0475 represents a significant security flaw in the procmail mail processing utility that has persisted for decades. This race condition affects the way procmail processes .procmailrc configuration files, creating a window of opportunity for local users to exploit system permissions and access files they should not be able to read. The issue specifically manifests when procmail handles the processing of these configuration files, where the timing of file operations creates a vulnerability that can be leveraged by malicious users.
The technical implementation of this vulnerability stems from a race condition in procmail's file handling mechanism during the processing of .procmailrc files. When a user runs procmail with a .procmailrc configuration file, the utility creates temporary files and performs operations that can be manipulated by an attacker. The race condition occurs between the time procmail checks for the existence of a file and the time it actually opens or reads that file, allowing a local attacker to replace or modify the target file during this brief window. This flaw is classified as a CWE-362 race condition vulnerability, where concurrent operations can result in unpredictable behavior and security breaches. The flaw is particularly dangerous because it allows privilege escalation within the context of the user running procmail, enabling access to files that would normally be restricted.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates a persistent security risk for systems running procmail. Local users who can manipulate the .procmailrc file or related temporary files can gain access to sensitive information that should remain protected. This includes potentially confidential emails, system configuration files, or other user data that the procmail process is authorized to access. The vulnerability affects any system where procmail is installed and used, particularly in multi-user environments where different users may have varying levels of access to system resources. According to ATT&CK framework, this represents a privilege escalation technique that can be categorized under T1068, 'Exploitation for Privilege Escalation', and T1566, 'Phishing for Information', as it can be used to gain unauthorized access to sensitive data that might otherwise be protected by proper file permissions.
Mitigation strategies for this vulnerability require immediate attention and system hardening measures. The most effective approach involves updating to a patched version of procmail that addresses the race condition in file handling operations. System administrators should ensure that all procmail installations are running the latest stable version with security patches applied. Additionally, proper file permissions and ownership controls should be enforced for .procmailrc files and related temporary files to prevent unauthorized modification. The principle of least privilege should be applied when configuring procmail, limiting the access rights of the procmail process to only what is necessary for its operation. Organizations should also implement monitoring for suspicious file access patterns and consider using file integrity monitoring tools to detect unauthorized modifications to critical configuration files. The vulnerability highlights the importance of proper synchronization mechanisms in file operations and demonstrates how seemingly simple race conditions can have serious security implications. Regular security audits of mail processing utilities and configuration management practices should be conducted to identify and remediate similar vulnerabilities in other system components.