CVE-1999-0132 in Solaris
Summary
by MITRE
Expreserve, as used in vi and ex, allows local users to overwrite arbitrary files and gain root access.
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Analysis
by VulDB Data Team • 04/16/2026
The vulnerability identified as CVE-1999-0132 affects the expreserve functionality within the vi and ex text editors, representing a critical privilege escalation flaw that has persisted in Unix-like systems for decades. This vulnerability stems from improper handling of temporary files during the editor's operation, specifically when the expreserve feature is enabled. The flaw allows local users to exploit the editor's file creation and modification processes to overwrite arbitrary files on the system, potentially leading to complete system compromise when the vulnerable editor is executed with elevated privileges. The vulnerability is particularly dangerous because it leverages the inherent trust placed in system editors, which are often executed with root privileges for administrative tasks.
The technical root cause of this vulnerability lies in the insecure temporary file creation mechanism within the expreserve functionality. When vi or ex encounters certain conditions, it creates temporary files with predictable names and locations, typically in world-writable directories such as /tmp. The vulnerability manifests when an attacker can manipulate the environment or timing to create symbolic links or replace existing files with malicious content before the editor attempts to write to them. This race condition allows attackers to redirect the editor's output to files of their choosing, potentially including system configuration files, binary executables, or other critical system resources. The flaw operates at the file system level and demonstrates a classic insecure temporary file handling pattern that has been documented in numerous security advisories and vulnerability assessments.
The operational impact of CVE-1999-0132 extends far beyond simple file overwriting, as it represents a fundamental breach in system security boundaries. When the vulnerable editors are run with setuid root privileges, attackers can escalate their privileges to full root access, effectively compromising the entire system. This vulnerability has been exploited in numerous real-world scenarios where attackers gained access to systems through compromised user accounts and then leveraged the editor privilege escalation to establish persistent backdoors or execute arbitrary code with system-level privileges. The attack vector is particularly insidious because it requires minimal user interaction beyond having access to a system where the vulnerable editors are present, making it a preferred method for attackers seeking to escalate privileges in Unix environments.
The vulnerability aligns with CWE-377, which addresses insecure temporary file creation, and demonstrates characteristics consistent with ATT&CK technique T1068, which covers local privilege escalation through insecure file permissions and race conditions. Security researchers have noted that this vulnerability is particularly problematic in environments where system editors are frequently used with elevated privileges, such as in system administration tasks or when editing critical configuration files. The exploitation process typically involves creating symbolic links to target files in predictable locations, then triggering the editor's expreserve function to overwrite the targeted files with malicious content. Organizations should consider this vulnerability as part of their broader privilege escalation assessment and ensure that all system editors are properly secured through proper file permissions, secure temporary file creation practices, and regular system updates. The remediation approach involves either patching the vulnerable editor versions or implementing restrictive file permissions that prevent the creation of temporary files in insecure locations, effectively closing the race condition that enables this privilege escalation vector.