CVE-2021-41072 : Vulnerability Insights and Analysis
Learn about CVE-2021-41072, a Directory Traversal vulnerability in Squashfs-Tools 4.5 allowing unsquashfs to write through a symbolic link to unintended locations in the filesystem. Find mitigation steps and preventive measures.
CVE-2021-41072 involves a Directory Traversal vulnerability in Squashfs-Tools 4.5 that can lead to unsquashfs writing through a symbolic link elsewhere in the filesystem.
Understanding CVE-2021-41072
What is CVE-2021-41072?
This CVE refers to the squashfs_opendir function in unsquash-2.c in Squashfs-Tools 4.5, allowing Directory Traversal. By including a symbolic link and corresponding contents under the same filename in a crafted squashfs filesystem, an attacker can manipulate unsquashfs to create a symbolic link pointing outside the intended directory and then write through the link to another location in the filesystem.
The Impact of CVE-2021-41072
An attacker exploiting this vulnerability can potentially write files to unintended locations on the filesystem, leading to unauthorized data access or manipulation.
Technical Details of CVE-2021-41072
Vulnerability Description
The issue arises from unsquashfs not properly handling symbolic links in certain crafted squashfs filesystems, allowing malicious actors to perform Directory Traversal attacks.
Affected Systems and Versions
- Vendor: n/a
- Product: n/a
- Versions Affected: All versions
Exploitation Mechanism
- Craft a squashfs filesystem with a symbolic link and corresponding content under the same file name.
- Unsquash the filesystem, causing unsquashfs to create a symbolic link pointing outside the intended directory.
- Write through the link, enabling the attacker to modify files in unintended locations.
Mitigation and Prevention
Immediate Steps to Take
- Update Squashfs-Tools to the latest version available.
- Avoid using untrusted squashfs filesystems.
- Implement strict file system access controls.
Long-Term Security Practices
- Regularly monitor security mailing lists for updates on Squashfs vulnerabilities.
- Conduct security assessments and penetration testing on filesystem handling mechanisms.
- Train personnel on secure filesystem handling best practices.
Patching and Updates
- Apply patches and updates provided by the Squashfs-Tools project to address this vulnerability.