CVE-2006-5297 in mail client
Summary
by MITRE
Race condition in the safe_open function in the Mutt mail client 1.5.12 and earlier, when creating temporary files in an NFS filesystem, allows local users to overwrite arbitrary files due to limitations of the use of the O_EXCL flag on NFS filesystems.
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Analysis
by VulDB Data Team • 04/24/2026
The vulnerability described in CVE-2006-5297 represents a critical race condition flaw within the Mutt email client version 1.5.12 and earlier implementations. This issue specifically manifests in the safe_open function when handling temporary file creation on Network File System (NFS) mounted filesystems. The fundamental problem arises from the inherent limitations of how the O_EXCL flag operates within NFS environments, creating a window of opportunity for malicious local users to exploit the system. The race condition occurs because the NFS implementation does not guarantee atomic behavior for the combination of file existence checks and creation operations that the safe_open function relies upon.
The technical exploitation of this vulnerability leverages the specific behavior of NFS filesystems where the O_EXCL flag does not provide the same atomic guarantees as it does on local filesystems. When Mutt creates temporary files, it first checks if the file exists and then attempts to create it exclusively. However, on NFS, between the existence check and the actual creation, another process or user can potentially create a symbolic link or file with the same name, effectively hijacking the intended file creation process. This flaw is particularly dangerous because it allows attackers to manipulate the temporary file creation process and ultimately overwrite arbitrary files on the system with potentially elevated privileges. The vulnerability is classified under CWE-367 which specifically addresses Time-of-Check to Time-of-Use (TOCTOU) race conditions, a well-documented weakness in system security design patterns.
The operational impact of this vulnerability extends beyond simple file overwriting capabilities as it provides local attackers with a method to potentially escalate privileges or cause denial of service conditions. When Mutt processes emails or handles attachments, it creates temporary files that may contain sensitive information or be used for system operations. An attacker could exploit this race condition to replace critical system files, configuration files, or even executable components with malicious versions, potentially leading to privilege escalation or system compromise. The vulnerability is particularly concerning in multi-user environments where NFS is commonly used for shared storage, as it allows any local user to potentially exploit this weakness to gain unauthorized access to system resources. The attack vector is relatively straightforward and does not require complex network access or sophisticated exploitation techniques, making it a significant security concern for organizations using Mutt with NFS storage.
Mitigation strategies for this vulnerability should focus on both immediate patching and system hardening measures. The most effective solution involves upgrading to Mutt versions 1.5.13 or later, where the race condition has been addressed through improved file creation handling and proper synchronization mechanisms. Organizations should also consider implementing additional security controls such as restricting temporary file creation permissions and using more secure temporary file creation methods that do not rely on the vulnerable O_EXCL flag behavior. System administrators should review NFS mount options to ensure appropriate security settings are in place and consider alternative filesystems for sensitive operations where race conditions are less likely to occur. The ATT&CK framework would categorize this vulnerability under privilege escalation techniques, specifically focusing on the use of race conditions to manipulate file system operations, with potential implications for persistence and privilege escalation within the target environment.