CVE-2001-0125 in exmh
Summary
by MITRE
exmh 2.2 and earlier allows local users to overwrite arbitrary files via a symlink attack on the exmhErrorMsg temporary file.
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Analysis
by VulDB Data Team • 07/19/2019
The vulnerability described in CVE-2001-0125 represents a classic file system security flaw affecting the exmh email client version 2.2 and earlier. This issue stems from improper handling of temporary files during error reporting operations, creating a predictable race condition that malicious local users can exploit to overwrite arbitrary files on the system. The exmhErrorMsg temporary file serves as a critical component in the application's error handling mechanism, but its insecure creation process leaves it vulnerable to symbolic link attacks that can be leveraged by attackers with local access to the system.
The technical flaw manifests when the exmh application creates a temporary error message file named exmhErrorMsg without proper security checks or atomic file creation mechanisms. This temporary file is typically created in a world-writable directory such as /tmp, making it susceptible to symlink attacks where an attacker can establish a symbolic link with the same name before the legitimate application creates the actual file. When the application subsequently writes to what it believes is the legitimate temporary file, it actually writes to the attacker-controlled target file, enabling arbitrary file overwrite operations. This vulnerability directly maps to CWE-377, which identifies insecure temporary file creation practices, and CWE-378, which addresses the creation of temporary files with insecure permissions.
The operational impact of this vulnerability extends beyond simple file overwrites, as it can be exploited to escalate privileges or compromise system integrity. Local attackers can leverage this weakness to replace critical system files, configuration files, or even binaries with malicious versions, potentially leading to privilege escalation or persistent backdoor access. The attack requires local system access and knowledge of the application's temporary file naming conventions, making it particularly dangerous in multi-user environments where attackers may have limited access but can still manipulate the file system. This type of vulnerability aligns with ATT&CK technique T1059.007 for execution through command and script interpreter, as attackers can use the compromised files to execute malicious code with elevated privileges.
Mitigation strategies for CVE-2001-0125 should focus on implementing secure temporary file creation practices and restricting file system permissions. System administrators should immediately upgrade to exmh version 2.3 or later, which addresses this vulnerability through proper temporary file handling mechanisms. Additionally, the application should be configured to create temporary files with restrictive permissions and use atomic file creation methods that prevent symbolic link attacks. The principle of least privilege should be enforced by ensuring that temporary files are created in secure directories with appropriate access controls. Security monitoring should include detection of suspicious temporary file creation patterns and unauthorized symbolic link modifications. Organizations should also consider implementing file integrity monitoring solutions to detect unauthorized changes to critical system files that could result from exploitation of this vulnerability.