CVE-2026-63812
Received Received - Intake

F2FS Inode Extent Cache Stale Data Vulnerability

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: fix incorrect FI_NO_EXTENT handling in __destroy_extent_node() When __destroy_extent_node() sets the inode flag FI_NO_EXTENT, it does not reset the length of the largest extent to 0 and update the inode folio. Since modifications to the extent tree are disallowed afterward, the cached largest extent may become stale. This can trigger the following error in xfstests generic/388: F2FS-fs (dm-0): sanity_check_extent_cache: inode (ino=1761) extent info [220057, 57, 6] is incorrect, run fsck to fix In the f2fs_drop_inode path, __destroy_extent_node() does not need to guarantee that et->node_cnt is 0, because concurrency with writeback is expected in this path, and writeback may update the extent cache. This patch reverts commit ed78aeebef05 ("f2fs: fix node_cnt race between extent node destroy and writeback"), and remove the unnecessary zero check of et->node_cnt.

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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-2026-63812
EUVD
EUVD-2026-45478

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
linux linux_kernel *
linux kernel *
linux_kernel f2fs *

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves incorrect handling of the FI_NO_EXTENT flag in the f2fs file system. When the __destroy_extent_node function sets this flag, it fails to reset the largest extent length to zero or update the inode folio. This leaves the cached extent information stale, which can cause errors during file system checks and potentially corrupt data.

Detection Guidance

This vulnerability is specific to the Linux kernel's F2FS filesystem and may trigger errors in xfstests generic/388. Detection involves checking kernel logs for the error message: 'sanity_check_extent_cache: inode (ino=X) extent info [Y, Z, W] is incorrect, run fsck to fix'. Use 'dmesg | grep -i f2fs' or 'journalctl -k | grep -i f2fs' to search for these errors.

Impact Analysis

This vulnerability may lead to file system corruption or errors during operations like xfstests. Users could experience data inconsistencies, crashes, or require file system repairs. Systems using the f2fs file system are particularly affected.

Compliance Impact

This vulnerability affects file system integrity in the Linux kernel, which could lead to data corruption or loss if the extent cache becomes stale. For compliance standards like GDPR or HIPAA, which require data integrity and availability, this could result in non-compliance if systems relying on f2fs experience data corruption or unavailability due to this issue.

Mitigation Strategies

Apply the kernel patch that resolves this issue. If patching is not immediately possible, consider disabling the F2FS filesystem or avoiding its use until the patch is applied. Run 'fsck' on affected filesystems to correct any potential corruption.

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