CVE-2024-35948 in Linux
Summary
by MITRE • 05/20/2024
In the Linux kernel, the following vulnerability has been resolved:
bcachefs: Check for journal entries overruning end of sb clean section
Fix a missing bounds check in superblock validation.
Note that we don't yet have repair code for this case - repair code for individual items is generally low priority, since the whole superblock is checksummed, validated prior to write, and we have backups.
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Analysis
by VulDB Data Team • 11/18/2025
The vulnerability identified as CVE-2024-35948 affects the Linux kernel's bcachefs filesystem implementation and represents a critical bounds checking flaw in superblock validation mechanisms. This issue specifically targets the journal entries handling within the superblock structure, where the system fails to properly validate that journal entries do not overflow beyond the designated end of the superblock clean section. The vulnerability stems from inadequate input validation during the superblock processing phase, creating a potential attack surface where maliciously crafted data could cause memory corruption or system instability.
The technical flaw manifests as a missing bounds check that should prevent journal entries from extending beyond the allocated superblock clean section boundaries. This type of vulnerability falls under the CWE-129 weakness category, which encompasses improper validation of array indices and buffer overflows in kernel space operations. When the bcachefs subsystem processes superblock data, it relies on the integrity of the superblock structure to maintain filesystem consistency and prevent unauthorized modifications to critical metadata. The absence of this validation check creates a scenario where an attacker could potentially manipulate journal entries to overwrite adjacent memory regions or corrupt superblock metadata.
From an operational impact perspective, this vulnerability poses significant risks to system stability and data integrity within environments utilizing bcachefs filesystems. The potential consequences include filesystem corruption, system crashes, or in more severe scenarios, privilege escalation opportunities that could allow attackers to gain elevated system privileges. The vulnerability affects systems running Linux kernels that incorporate the bcachefs filesystem implementation, particularly those where the superblock validation process is executed without proper bounds checking. The impact is amplified by the fact that superblock data is critical for filesystem operations and contains essential metadata that governs filesystem behavior and consistency.
The mitigation strategy for this vulnerability involves applying the kernel patch that implements proper bounds checking in the superblock validation process. System administrators should prioritize updating their Linux kernel versions to include the fix for CVE-2024-35948, as the vulnerability exists in the kernel's core filesystem handling mechanisms. While the kernel developers have noted that repair code for individual items is a low priority due to the comprehensive checksumming and backup mechanisms already present in the superblock structure, organizations should still implement the patch to prevent potential exploitation scenarios. The fix specifically addresses the missing validation that would have otherwise allowed journal entries to overrun the superblock clean section boundaries, thereby maintaining the integrity of filesystem metadata and preventing potential memory corruption issues. Security teams should monitor for any potential exploitation attempts targeting this specific kernel vulnerability, particularly in environments where bcachefs filesystems are deployed and where attackers might attempt to leverage such flaws for unauthorized system access or data manipulation.