CVE-2006-3123 in Cryptographic File System
Summary
by MITRE
Multiple integer overflows in the (1) dodecrypt and (2) doencrypt functions in cfs_fh.c in cfsd in Matt Blaze Cryptographic File System (CFS) 1.4.1 before Debian GNU/Linux package 1.4.1-17 allow local users to cause a denial of service (daemon crash) by appending data to a file that is larger than 2 Gb.
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Analysis
by VulDB Data Team • 07/21/2019
The vulnerability identified as CVE-2006-3123 affects the Matt Blaze Cryptographic File System (CFS) version 1.4.1, specifically targeting the dodecrypt and doencrypt functions within the cfs_fh.c file that operates within the cfsd daemon. This issue represents a critical security flaw that enables local attackers to disrupt system operations through carefully crafted file manipulation techniques. The vulnerability stems from improper handling of integer values during cryptographic file operations, creating conditions where the system fails to properly validate file size parameters.
The technical implementation of this vulnerability manifests through integer overflow conditions in the cryptographic file handling functions. When local users append data to files exceeding the 2 gigabyte threshold, the system's integer arithmetic operations overflow, causing the cfsd daemon to crash and terminate unexpectedly. This occurs because the functions fail to properly validate that file operations remain within the bounds of their integer data type limitations. The overflow conditions specifically affect the internal counters and size calculations used during encryption and decryption processes, leading to unpredictable behavior and system instability.
The operational impact of this vulnerability extends beyond simple denial of service, as it can compromise the overall reliability and availability of cryptographic file systems. The daemon crash resulting from this vulnerability can disrupt ongoing file operations, potentially leading to data loss or corruption during critical cryptographic processes. System administrators face challenges in maintaining service availability when local users can intentionally trigger daemon failures through legitimate file manipulation activities. This vulnerability particularly affects environments where CFS is deployed as a critical file system component, as the daemon crash can cascade into broader system instability.
The vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions, and demonstrates characteristics consistent with the ATT&CK technique T1499.004 for network denial of service. The issue occurs at the system level within the cryptographic file system daemon, making it particularly dangerous for environments requiring persistent file access and encryption services. Organizations using CFS implementations should consider this vulnerability as part of their broader security posture assessment, particularly when evaluating the robustness of cryptographic file handling mechanisms. The fix typically involves updating to the Debian GNU/Linux package version 1.4.1-17 or later, which includes proper integer validation and bounds checking mechanisms to prevent the overflow conditions that trigger daemon crashes.
This vulnerability represents a classic example of how seemingly minor implementation flaws in cryptographic systems can lead to significant operational disruptions. The integer overflow conditions in CFS demonstrate the importance of robust input validation and proper boundary checking in security-critical software components. System administrators should implement monitoring for daemon crashes and consider additional security measures to prevent local users from exploiting such vulnerabilities, particularly in multi-user environments where privilege escalation risks are elevated. The remediation process requires careful consideration of the broader system impact, as updating cryptographic file system components may require coordination across multiple services and applications that depend on CFS functionality.