CVE-2024-40902 in Linux
Summary
by MITRE • 07/12/2024
In the Linux kernel, the following vulnerability has been resolved:
jfs: xattr: fix buffer overflow for invalid xattr
When an xattr size is not what is expected, it is printed out to the kernel log in hex format as a form of debugging. But when that xattr size is bigger than the expected size, printing it out can cause an access off the end of the buffer.
Fix this all up by properly restricting the size of the debug hex dump in the kernel log.
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Analysis
by VulDB Data Team • 09/27/2024
The vulnerability identified as CVE-2024-40902 affects the Linux kernel's JFS (Journaling File System) implementation and represents a buffer overflow condition that occurs during extended attribute debugging operations. This flaw exists within the kernel's handling of invalid extended attributes where the system attempts to log diagnostic information about malformed attribute sizes. The issue specifically manifests when the system encounters extended attributes with sizes that exceed expected parameters, creating a scenario where debug output generation can access memory beyond the allocated buffer boundaries. Such buffer overflows represent a critical class of memory safety vulnerabilities that can potentially lead to system instability or information disclosure.
The technical implementation of this vulnerability stems from improper bounds checking during kernel log output operations for extended attribute debugging. When the JFS subsystem processes extended attributes, it includes logic to output attribute sizes in hexadecimal format for debugging purposes. However, the current implementation fails to properly constrain the maximum size of data that can be printed to kernel logs, allowing for potential buffer overflows when attribute sizes exceed predefined limits. This condition directly corresponds to CWE-121, which describes stack-based buffer overflow vulnerabilities, and CWE-122, which addresses heap-based buffer overflow scenarios. The vulnerability operates at the kernel level where memory management is critical, making any buffer overflow potentially exploitable for privilege escalation or denial of service attacks.
The operational impact of CVE-2024-40902 extends beyond simple system instability to encompass potential security implications for systems utilizing JFS filesystems. When triggered, the buffer overflow can cause kernel memory corruption, leading to system crashes, unpredictable behavior, or potentially allowing attackers to extract sensitive kernel memory information through carefully crafted extended attribute operations. Systems running Linux kernels with JFS support are particularly vulnerable, as the vulnerability is present in the core filesystem handling code where extended attribute operations are processed. The debug output mechanism, while intended to aid in troubleshooting, becomes a vector for memory corruption when dealing with malformed extended attributes. This vulnerability affects the kernel's ability to maintain memory integrity during extended attribute processing and can result in system-wide instability.
Mitigation strategies for CVE-2024-40902 focus primarily on applying the official kernel patch that properly restricts the size of debug hex dumps in kernel logs. System administrators should prioritize updating their Linux kernel installations to versions containing the fix, which typically involves implementing proper bounds checking before printing extended attribute sizes to kernel logs. The patch ensures that debug output operations respect buffer boundaries and prevent access beyond allocated memory regions. Organizations should also implement monitoring for unusual kernel log entries that might indicate exploitation attempts or system instability related to extended attribute operations. Additionally, maintaining up-to-date system patches aligns with ATT&CK technique T1068, which involves the exploitation of system privileges, and addresses the broader category of kernel-level vulnerabilities that can be leveraged for privilege escalation or system compromise. Regular security assessments of filesystem configurations and extended attribute usage patterns should also be conducted to identify potential attack vectors.