CVE-2026-63816
Received Received - Intake

Use-After-Free in Linux Kernel F2FS Atomic Inode

Publication date: 2026-07-19

Last updated on: 2026-07-19

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode - ioctl(F2FS_IOC_GARBAGE_COLLECT_RANGE) - shrink - f2fs_gc - gc_data_segment - ra_data_block(cow_inode) - mapping = F2FS_I(inode)->atomic_inode->i_mapping : f2fs_is_cow_file(cow_inode) is true - f2fs_evict_inode(atomic_inode) - clear_inode_flag(fi->cow_inode, FI_COW_FILE) - F2FS_I(fi->cow_inode)->atomic_inode = NULL ... - truncate_inode_pages_final(atomic_inode) - f2fs_grab_cache_folio(mapping) : create folio in atomic_inode->mapping - clear_inode(atomic_inode) - BUG_ON(atomic_inode->i_data.nrpages) We need to add a reference on fi->atomic_inode before using its mapping field during garbage collection, otherwise, it will cause UAF issue.

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Meta Information

Published
2026-07-19
Last Modified
2026-07-19
Generated
2026-07-20
AI Q&A
2026-07-19
EPSS Evaluated
N/A
NVD
CVE-2026-63816
EUVD
EUVD-2026-45482

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
linux kernel *
linux linux_kernel *

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Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a Use-After-Free (UAF) vulnerability in the Linux kernel's F2FS (Flash-Friendly File System) atomic write feature. It occurs during garbage collection when the atomic_inode mapping field is accessed after the inode has been freed. The issue stems from not holding a reference to fi->atomic_inode before using its mapping during garbage collection operations.

Detection Guidance

This vulnerability is specific to the Linux kernel's F2FS filesystem and requires kernel-level detection. Check your kernel version and F2FS module status. Use commands like 'uname -a' to verify kernel version and 'lsmod | grep f2fs' to check if F2FS is loaded. Monitor kernel logs for crashes or errors related to f2fs_gc or atomic_inode operations.

Impact Analysis

This vulnerability could allow an attacker to cause a system crash or potentially execute arbitrary code with kernel privileges. It affects systems using F2FS with atomic write support, potentially leading to denial-of-service conditions or privilege escalation if exploited.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards as it is a technical flaw in the Linux kernel's file system handling. Compliance impacts would depend on how the affected system is used and whether it processes regulated data.

Mitigation Strategies

Apply the latest kernel patches from your distribution to resolve this issue. If patches are unavailable, consider disabling the F2FS filesystem module temporarily by running 'modprobe -r f2fs'. Avoid using F2FS features that trigger garbage collection (e.g., ioctl F2FS_IOC_GARBAGE_COLLECT_RANGE) until patched.

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