CVE-2026-64361 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
hfs/hfsplus: fix u32 overflow in check_and_correct_requested_length
check_and_correct_requested_length() compares (off + len) against node_size using u32 arithmetic. When the caller passes a large len value (e.g. from an underflowed subtraction in hfs_brec_remove()), off + len can wrap past 2^32 and produce a small result, causing the bounds check to pass when it should fail.
For example, with off=14 and len=0xFFFFFFF2 (underflowed from data_off - keyoffset - size in hfs_brec_remove), off + len wraps to 6, which is less than a typical node_size of 512, so the check passes and the subsequent memmove reads ~4GB past the node buffer.
Fix this by widening the addition to u64 before comparing against node_size. This prevents the u32 wrap while keeping the logic straightforward.
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Analysis
by VulDB Data Team • 07/25/2026
The vulnerability in question affects the Linux kernel's HFS and HFS+ filesystem implementations, specifically within the check_and_correct_requested_length function that handles bounds checking for file operations. This issue represents a classic unsigned integer overflow condition that can lead to memory corruption and potential privilege escalation. The flaw occurs when processing record removal operations in HFS+ filesystems where the function performs arithmetic operations using 32-bit unsigned integers without proper overflow detection mechanisms.
The technical implementation of this vulnerability stems from improper handling of arithmetic operations within the hfs_brec_remove() function which calculates a length value that can underflow. When this underflowed value is passed to check_and_correct_requested_length(), the function performs an addition operation using u32 arithmetic where off + len can exceed the maximum value representable by 32-bit unsigned integers, causing the result to wrap around to a small positive value. This wrapping behavior bypasses the intended bounds checking mechanism that should prevent access beyond valid memory boundaries.
The operational impact of this vulnerability extends beyond simple memory corruption as it creates conditions where malicious actors could potentially exploit the memory overwrite to execute arbitrary code or escalate privileges within the kernel space. The specific example demonstrates how an off value of 14 combined with a large len value of 0xFFFFFFF2 results in a wrapped sum of only 6, which is significantly smaller than typical node_size values of 512 bytes. This allows subsequent memmove operations to read approximately 4GB past the legitimate node buffer boundaries, creating opportunities for data corruption or code execution.
This vulnerability type aligns with CWE-191, which describes unsigned integer underflow conditions, and can be mapped to ATT&CK technique T1068, involving exploitation of privilege escalation vulnerabilities. The fix implemented addresses this by widening the arithmetic operation from u32 to u64 before performing the comparison against node_size, effectively preventing the wraparound behavior while maintaining the logical integrity of the bounds checking mechanism. This remediation approach follows established security principles for integer overflow prevention and demonstrates proper defensive programming practices that align with industry standards for kernel security hardening.
The mitigation strategy requires updating the Linux kernel to versions containing this specific fix, as the vulnerability exists at the filesystem driver level and affects all systems running affected kernel versions. Organizations should prioritize patching their systems given the potential for privilege escalation and memory corruption that this vulnerability enables. The solution's simplicity and directness in addressing the root cause makes it an effective defense against exploitation attempts while maintaining system functionality and performance characteristics of the HFS+ filesystem implementation.