CVE-2012-5375 in Linux
Summary
by MITRE
The CRC32C feature in the Btrfs implementation in the Linux kernel before 3.8-rc1 allows local users to cause a denial of service (prevention of file creation) by leveraging the ability to write to a directory important to the victim, and creating a file with a crafted name that is associated with a specific CRC32C hash value.
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Analysis
by VulDB Data Team • 09/29/2024
The vulnerability described in CVE-2012-5375 represents a significant flaw in the Btrfs file system implementation within the Linux kernel ecosystem. This issue specifically targets the CRC32C checksum calculation mechanism that Btrfs employs for data integrity verification. The vulnerability arises from the way the kernel handles file creation operations when specific directory permissions and file naming conventions are manipulated by local users. The flaw exists in kernel versions prior to 3.8-rc1, indicating a window of exposure where systems utilizing Btrfs file systems were susceptible to targeted denial of service attacks.
The technical exploitation of this vulnerability hinges on the manipulation of directory write permissions and the creation of files with carefully crafted names that generate specific CRC32C hash values. When a local attacker with write access to a directory can influence the file creation process, they can construct filenames that trigger problematic CRC32C calculations within the Btrfs implementation. This manipulation causes the kernel's file system layer to enter an inconsistent state where subsequent file creation operations become impossible, effectively preventing legitimate users from creating new files in the affected directory. The attack vector leverages the fundamental relationship between file naming, checksum generation, and kernel memory management within the Btrfs subsystem.
The operational impact of this vulnerability extends beyond simple service disruption, as it represents a sophisticated denial of service mechanism that can be weaponized against specific targets. The vulnerability's classification as a local privilege escalation issue means that any user with write permissions to a target directory can potentially render the entire directory inaccessible to other users, including system administrators. This creates a scenario where attackers can systematically compromise file system functionality without requiring elevated privileges, making it particularly dangerous in multi-user environments. The issue demonstrates how seemingly benign file system features can be exploited to create persistent service interruptions that may require system restarts or manual intervention to resolve.
From a cybersecurity perspective, this vulnerability aligns with several ATT&CK framework techniques including privilege escalation through exploitation of system vulnerabilities and denial of service attacks. The flaw represents a classic example of how cryptographic checksum implementations can introduce unexpected behavior when not properly validated against malicious inputs. Organizations implementing Btrfs file systems should prioritize immediate patching to kernel versions 3.8-rc1 or later, as the vulnerability provides no legitimate security benefit and creates a clear attack surface for local users. System administrators should also implement monitoring for unusual file creation patterns and consider implementing additional directory-level access controls to limit the scope of potential exploitation. The vulnerability serves as a reminder of the critical importance of thorough validation of all input parameters, particularly in cryptographic implementations, and underscores the need for comprehensive security testing of file system components.