CVE-2025-68796
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2026-01-13

Last updated on: 2026-01-19

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid updating zero-sized extent in extent cache As syzbot reported: F2FS-fs (loop0): __update_extent_tree_range: extent len is zero, type: 0, extent [0, 0, 0], age [0, 0] ------------[ cut here ]------------ kernel BUG at fs/f2fs/extent_cache.c:678! 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~bpo12+1 04/01/2014 RIP: 0010:__update_extent_tree_range+0x13bc/0x1500 fs/f2fs/extent_cache.c:678 Call Trace: <TASK> f2fs_update_read_extent_cache_range+0x192/0x3e0 fs/f2fs/extent_cache.c:1085 f2fs_do_zero_range fs/f2fs/file.c:1657 [inline] f2fs_zero_range+0x10c1/0x1580 fs/f2fs/file.c:1737 f2fs_fallocate+0x583/0x990 fs/f2fs/file.c:2030 vfs_fallocate+0x669/0x7e0 fs/open.c:342 ioctl_preallocate fs/ioctl.c:289 [inline] file_ioctl+0x611/0x780 fs/ioctl.c:-1 do_vfs_ioctl+0xb33/0x1430 fs/ioctl.c:576 __do_sys_ioctl fs/ioctl.c:595 [inline] __se_sys_ioctl+0x82/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f07bc58eec9 In error path of f2fs_zero_range(), it may add a zero-sized extent into extent cache, it should be avoided.
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Meta Information
Published
2026-01-13
Last Modified
2026-01-19
Generated
2026-05-07
AI Q&A
2026-01-14
EPSS Evaluated
2026-05-05
NVD
CVE-2025-68796
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux kernel *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is in the Linux kernel's F2FS filesystem. It occurs because the system may add a zero-sized extent into the extent cache during an error path in the f2fs_zero_range() function. This improper update can cause a kernel BUG and crash, as the extent length is zero, which should be avoided.


How can this vulnerability impact me? :

The vulnerability can cause the Linux kernel to crash (kernel BUG) when handling certain filesystem operations on F2FS. This can lead to system instability, potential data loss, or denial of service due to the kernel panic triggered by the zero-sized extent update.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by monitoring kernel logs for specific error messages related to the f2fs filesystem. Look for kernel BUG messages mentioning '__update_extent_tree_range' and zero-sized extent updates in the extent cache. You can use the following command to check the kernel log for such errors: sudo dmesg | grep -i 'f2fs.*extent len is zero' or sudo journalctl -k | grep -i 'f2fs.*extent len is zero' These commands help identify if the system has encountered the bug described in the vulnerability.


What immediate steps should I take to mitigate this vulnerability?

The immediate mitigation step is to update the Linux kernel to a version where this vulnerability has been fixed. The fix avoids updating zero-sized extents in the extent cache in the f2fs filesystem. Until the kernel is updated, avoid operations that trigger f2fs zero range updates, such as fallocate or ioctl operations on f2fs filesystems that might cause this bug to manifest.


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