# CVE-2025-40137: f2fs: fix to truncate first page in error path of f2fs_truncate()

> A local attacker can trigger a kernel bug in the F2FS filesystem driver by mounting a corrupted image, causing a system crash.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Nov 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-40137, DEBIAN-CVE-2025-40137, GHSA-g9j9-8gxh-gh9r, ROOT-OS-DEBIAN-11-CVE-2025-40137, ROOT-OS-DEBIAN-12-CVE-2025-40137, ROOT-OS-DEBIAN-13-CVE-2025-40137, ROOT-OS-UBUNTU-2204-CVE-2025-40137, ROOT-OS-UBUNTU-2404-CVE-2025-40137, UBUNTU-CVE-2025-40137

## What is CVE-2025-40137?

CVE-2025-40137 is a denial of service vulnerability in Linux, published on 12 Nov 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix to truncate first page in error path of f2fs_truncate()

syzbot reports a bug as below:

loop0: detected capacity change from 0 to 40427
F2FS-fs (loop0): Wrong SSA boundary, start(3584) end(4096) blocks(3072)
F2FS-fs (loop0): Can't find valid F2FS filesystem in 1th superblock
F2FS-fs (loop0): invalid crc value
F2FS-fs (loop0): f2fs_convert_inline_folio: corrupted inline inode ino=3, i_addr[0]:0x1601, run fsck to fix.
------------[ cut here ]------------
kernel BUG at fs/inode.c:753!
RIP: 0010:clear_inode+0x169/0x190 fs/inode.c:753
Call Trace:
 <TASK>
 evict+0x504/0x9c0 fs/inode.c:810
 f2fs_fill_super+0x5612/0x6fa0 fs/f2fs/super.c:5047
 get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1692
 vfs_get_tree+0x8f/0x2b0 fs/super.c:1815
 do_new_mount+0x2a2/0x9e0 fs/namespace.c:3808
 do_mount fs/namespace.c:4136 [inline]
 __do_sys_mount fs/namespace.c:4347 [inline]
 __se_sys_mount+0x317/0x410 fs/namespace.c:4324
 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

During f2fs_evict_inode(), clear_inode() detects that we missed to truncate
all page cache before destorying inode, that is because in below path, we
will create page #0 in cache, but missed to drop it in error path, let's fix
it.

- evict
 - f2fs_evict_inode
  - f2fs_truncate
   - f2fs_convert_inline_inode
    - f2fs_grab_cache_folio
    : create page #0 in cache
    - f2fs_convert_inline_folio
    : sanity check failed, return -EFSCORRUPTED
  - clear_inode detects that inode->i_data.nrpages is not zero

## Which versions are affected by CVE-2025-40137?


## How do I fix CVE-2025-40137?

Apply the vendor's patch.

## Is CVE-2025-40137 being exploited?

There is no known exploitation of CVE-2025-40137 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40137 and fix it if it is affected.

What it is: CVE-2025-40137 is a denial of service vulnerability in Linux, published on 12 Nov 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-40137 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-40137/ (Markdown: https://insights.sbomify.com/CVE-2025-40137/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40137
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40137
- OSV: https://osv.dev/vulnerability/CVE-2025-40137

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40137/
Summaries are generated and may contain mistakes; the official description above is the record.