CVE-2001-0890 in SANE
Summary
by MITRE
Certain backend drivers in the SANE library 1.0.3 and earlier, as used in frontend software such as XSane, allows local users to modify files via a symlink attack on temporary files.
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Analysis
by VulDB Data Team • 06/04/2018
The vulnerability identified as CVE-2001-0890 represents a critical security flaw within the SANE (Scanner Access Now Easy) library version 1.0.3 and earlier implementations. This issue affects the backend drivers responsible for communicating with scanning hardware and demonstrates a classic race condition vulnerability that can be exploited through symbolic link manipulation. The SANE library serves as a middleware component that provides standardized access to various scanner devices across different operating systems, making it a fundamental component in scanning software ecosystems including XSane and other frontend applications. When these backend drivers create temporary files without proper security checks, they expose the system to potential unauthorized modifications.
The technical exploitation of this vulnerability occurs through a time-of-check to time-of-use race condition pattern where an attacker creates symbolic links to target files before the backend driver performs its operations. During the scanning process, the SANE backend drivers generate temporary files in predictable locations without verifying the ownership or type of existing files at the target location. This allows a local attacker to establish symbolic links pointing to sensitive system files such as configuration files, binaries, or privilege escalation targets. The attacker can then manipulate the backend driver's behavior to write data to these symbolic links, effectively modifying files that should remain protected. This type of vulnerability is categorized under CWE-367, which specifically addresses Time-of-Check to Time-of-Use race conditions, and aligns with ATT&CK technique T1068 which covers local privilege escalation through race conditions.
The operational impact of this vulnerability extends beyond simple file modification, as it can enable attackers to escalate privileges, compromise system integrity, and potentially gain persistent access to affected systems. Since the vulnerability exists in the backend drivers of the SANE library, any application that relies on this library for scanning operations becomes vulnerable, including desktop scanning applications, document management systems, and network scanning services. The local nature of the attack means that exploitation requires physical access or existing user-level credentials, but the potential for privilege escalation makes this particularly dangerous in multi-user environments where scanners are shared or accessible through network services. The vulnerability demonstrates a fundamental flaw in the security design of temporary file handling within the scanning ecosystem and represents a common pattern seen in legacy software implementations that predate modern security best practices.
Mitigation strategies for CVE-2001-0890 should focus on immediate patching of the SANE library to version 1.0.4 or later, which includes proper temporary file handling mechanisms that prevent symbolic link attacks. System administrators should implement additional security measures such as setting proper file permissions on temporary directories, using secure temporary file creation functions that verify file ownership, and implementing mandatory access controls through SELinux or similar security frameworks. The remediation process should also include reviewing all scanning applications that utilize the SANE library to ensure they are not vulnerable to similar race condition attacks. Security monitoring should be enhanced to detect suspicious file creation patterns and unauthorized modifications to system files. Organizations should also consider implementing network segmentation to limit access to scanning services and ensure that scanner interfaces are properly secured both physically and logically to prevent unauthorized users from exploiting this vulnerability through local access. The vulnerability serves as a reminder of the importance of secure coding practices, particularly around temporary file handling, and the need for regular security updates to address known vulnerabilities in widely-used system components.