CVE-2026-63819
Received Received - Intake

Kernel Bug in F2FS Filesystem Truncation Operation

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 to do sanity check on f2fs_get_node_folio_ra() kernel BUG at fs/f2fs/file.c:845! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI CPU: 0 UID: 0 PID: 5336 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:f2fs_do_truncate_blocks+0x1115/0x1140 fs/f2fs/file.c:845 Code: fc fc 90 0f 0b e8 8b 9d 9a fd 90 0f 0b e8 83 9d 9a fd 48 89 df 48 c7 c6 60 d1 1a 8c e8 54 f1 fc fc 90 0f 0b e8 6c 9d 9a fd 90 <0f> 0b e8 64 9d 9a fd 90 0f 0b 90 e9 93 fd ff ff e8 56 9d 9a fd 90 RSP: 0018:ffffc9000e4474c0 EFLAGS: 00010283 RAX: ffffffff842b1d34 RBX: 0000000000000003 RCX: 0000000000100000 RDX: ffffc9000f03a000 RSI: 0000000000035503 RDI: 0000000000035504 RBP: ffffc9000e447608 R08: ffff8880123b0000 R09: 0000000000000002 R10: 00000000fffffffe R11: 0000000000000002 R12: 0000000000000001 R13: 0000000000000000 R14: 1ffff92001c88ea0 R15: 00000000ffff039c FS: 00007f7e02ee36c0(0000) GS:ffff88808c887000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ff0305c4000 CR3: 0000000012d4c000 CR4: 0000000000352ef0 Call Trace: <TASK> f2fs_truncate_blocks+0x10a/0x300 fs/f2fs/file.c:882 f2fs_truncate+0x471/0x7c0 fs/f2fs/file.c:940 f2fs_evict_inode+0xa3f/0x1ac0 fs/f2fs/inode.c:907 evict+0x61e/0xb10 fs/inode.c:841 f2fs_fill_super+0x5f43/0x78f0 fs/f2fs/super.c:5224 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694 vfs_get_tree+0x92/0x2a0 fs/super.c:1754 fc_mount fs/namespace.c:1193 [inline] do_new_mount_fc fs/namespace.c:3758 [inline] do_new_mount+0x341/0xd30 fs/namespace.c:3834 do_mount fs/namespace.c:4167 [inline] __do_sys_mount fs/namespace.c:4383 [inline] __se_sys_mount+0x31d/0x420 fs/namespace.c:4360 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f count = ADDRS_PER_PAGE(dn.node_folio, inode); count -= dn.ofs_in_node; f2fs_bug_on(sbi, count < 0); The fuzz test will trigger above bug_on in f2fs. The root cause should be: in the corrupted inode, there is a direct node which has the same ino and nid in its footer, so in f2fs_do_truncate_blocks(), after f2fs_get_dnode_of_data() finds such dnode: 1) ADDRS_PER_PAGE(dn.node_folio, inode) will return 923 2) once dn.ofs_in_node points to addr[923, 1017] Then it will trigger the system panic. Let's introduce NODE_TYPE_NON_IXNODE to indicate current node should not be an inode or xattr node, and then use it in below path to detect inconsistent node chain in inode mapping table: - f2fs_do_truncate_blocks - f2fs_get_dnode_of_data - f2fs_get_node_folio_ra - __get_node_folio - f2fs_sanity_check_node_footer - case NODE_TYPE_NON_IXNODE -> check whether it is inode|xnode

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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-2026-63819
EUVD
EUVD-2026-45485

Affected Vendors & Products

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

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a Linux kernel vulnerability in the F2FS (Flash-Friendly File System) component. It causes a kernel panic due to a bug in the f2fs_do_truncate_blocks function. The issue occurs when a corrupted inode contains a direct node with matching inode and node IDs in its footer. This leads to an invalid calculation in f2fs_do_truncate_blocks, triggering a system crash with an invalid opcode error.

Detection Guidance

This vulnerability is specific to the Linux kernel's F2FS filesystem and requires kernel-level detection. Check kernel logs for f2fs-related errors or BUG messages using commands like 'dmesg | grep f2fs' or 'journalctl -k | grep f2fs'. Ensure your kernel is updated to a patched version.

Impact Analysis

This vulnerability can cause a system crash (kernel panic) when processing corrupted file system data. It may lead to data loss or denial of service if an attacker can trigger the bug. Systems using F2FS with untrusted file system data are most at risk.

Compliance Impact

This vulnerability is a Linux kernel flaw in the F2FS filesystem that causes a kernel panic due to corrupted inode handling. It does not directly impact data privacy or security controls required by GDPR or HIPAA. However, system crashes could lead to denial of service, potentially affecting availability of regulated data systems.

Mitigation Strategies

Update the Linux kernel to the latest stable version that includes the fix for CVE-2026-63819. Avoid using F2FS for critical data until patched. Monitor kernel logs for signs of exploitation or crashes.

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