# CVE-2025-68796: f2fs: fix to avoid updating zero-sized extent in extent cache

CVE-2025-68796 is fixed in linux on 1 platform, first by DEBIAN-CVE-2025-68796, released January 13, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2025-68796
- Priority: Routine
- CVSS: 5.0 (Moderate)
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jan 13, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-68796

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.162-1 | [DEBIAN-CVE-2025-68796](https://patchblox.com/security/data/fix/linux/debian-cve-2025-68796.md) | Jan 13, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.69-1 | [DEBIAN-CVE-2025-68796](https://patchblox.com/security/data/fix/linux/debian-cve-2025-68796.md) | Jan 13, 2026 |
| Linux | linux Debian 14 | 6.18.3-1 | [DEBIAN-CVE-2025-68796](https://patchblox.com/security/data/fix/linux/debian-cve-2025-68796.md) | Jan 13, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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