CVE-2001-1276 in Ispell
Summary
by MITRE
ispell before 3.1.20 allows local users to overwrite files of other users via a symlink attack on a temporary file.
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Analysis
by VulDB Data Team • 05/02/2019
The vulnerability described in CVE-2001-1276 represents a classic privilege escalation and file system manipulation issue affecting the ispell spell checking utility version 3.1.19 and earlier. This flaw enables local attackers to exploit a race condition in the temporary file creation process, allowing them to overwrite files belonging to other users on the same system. The vulnerability stems from inadequate handling of temporary files during the spell checking process, where ispell creates temporary files without proper security checks or atomic operations.
The technical implementation of this vulnerability involves a symbolic link attack against temporary files generated by ispell during its operation. When ispell processes documents, it creates temporary files in predictable locations that can be manipulated by local users. An attacker with access to the system can create symbolic links in the temporary file directories, pointing to files they wish to overwrite. When ispell subsequently creates its temporary files, it inadvertently writes to the target files through the symbolic link, effectively overwriting them with arbitrary content. This type of attack falls under the category of time-of-check to time-of-use race conditions as defined by CWE-367, where the system checks file permissions at one point and then operates on the file at a later point, creating an exploitable window.
The operational impact of this vulnerability extends beyond simple file overwrites, as it can potentially lead to privilege escalation and system compromise. An attacker could target critical system files, configuration files, or files belonging to other users with higher privileges. The vulnerability is particularly dangerous in multi-user environments where users may have varying levels of access rights. Attackers could overwrite system binaries, configuration files, or user data, potentially leading to denial of service, data corruption, or unauthorized access to sensitive information. This vulnerability directly relates to ATT&CK technique T1059.007 for executing malicious code through command-line interfaces and T1078 for gaining access through valid accounts.
Mitigation strategies for this vulnerability involve immediate patching of ispell to version 3.1.20 or later, which addressed the temporary file handling issue through proper security measures. System administrators should ensure that all instances of ispell are updated to secure versions and verify that temporary file directories have appropriate permissions and are not writable by untrusted users. Additional protective measures include implementing proper file system permissions, using secure temporary file creation methods that prevent symbolic link attacks, and conducting regular security audits of installed software packages. Organizations should also consider implementing monitoring solutions to detect suspicious file modification patterns and establish proper access controls to prevent unauthorized users from creating symbolic links in temporary directories. The vulnerability highlights the importance of secure coding practices in Unix-like systems and demonstrates how seemingly simple operations can create significant security risks when proper file system security measures are not implemented.