CVE-2015-4646 in squashfs
Summary
by MITRE
(1) unsquash-1.c, (2) unsquash-2.c, (3) unsquash-3.c, and (4) unsquash-4.c in Squashfs and sasquatch allow remote attackers to cause a denial of service (application crash) via a crafted input.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 11/29/2022
The vulnerability identified as CVE-2015-4646 affects the Squashfs and sasquatch file systems through multiple unsquash implementation files including unsquash-1.c, unsquash-2.c, unsquash-3.c, and unsquash-4.c. This issue represents a classic denial of service vulnerability that can be exploited remotely by attackers who craft malicious input files designed to trigger application crashes. The vulnerability specifically impacts the extraction functionality of these file systems where the unsquash utilities process compressed file structures and encounter malformed input that causes the applications to terminate unexpectedly.
The technical flaw stems from insufficient input validation within the Squashfs extraction utilities, particularly in how they handle malformed or crafted file system structures during the decompression process. When these utilities encounter specially constructed input files, they fail to properly validate the data structures and metadata within the squashfs format, leading to memory corruption or invalid memory access patterns that ultimately result in application crashes. This type of vulnerability falls under CWE-121, which describes stack-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read errors, as the malformed input can cause the applications to access memory locations outside of allocated buffers or beyond valid data boundaries.
The operational impact of this vulnerability extends beyond simple service disruption as it can be exploited by remote attackers without requiring authentication or elevated privileges. Attackers can craft malicious squashfs files that, when processed by vulnerable applications, will cause the target systems to crash and potentially become unavailable to legitimate users. This vulnerability affects systems that utilize Squashfs file systems for various purposes including embedded systems, Linux distributions, and containerized environments where these file systems are commonly employed for efficient storage and distribution of file structures. The remote exploitation capability makes this particularly dangerous as attackers can target systems through network-based delivery mechanisms without needing physical access.
Mitigation strategies for CVE-2015-4646 should focus on immediate patching of affected software versions and implementing input validation controls. Organizations should prioritize updating their Squashfs and sasquatch implementations to versions that contain proper input sanitization and error handling mechanisms. Additionally, network administrators should consider implementing file type restrictions and content filtering where these utilities are used, particularly in environments where untrusted input may be processed. The vulnerability demonstrates the importance of robust input validation as outlined in the ATT&CK framework under T1203, which covers exploitation for privilege escalation through malformed input handling. System administrators should also implement monitoring and alerting for unexpected application crashes or restarts that may indicate exploitation attempts, and consider deploying intrusion detection systems that can identify suspicious file processing patterns. Regular security assessments of file system utilities and containerized applications that rely on Squashfs functionality will help identify and remediate similar vulnerabilities before they can be exploited in production environments.