# CVE-2025-37739: f2fs: fix to avoid out-of-bounds access in f2fs_truncate_inode_blocks()

> A local attacker can trigger an out-of-bounds memory access in the Linux kernel's f2fs filesystem, potentially causing a system crash.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H`)
- **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:** 1 May 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-37739, DEBIAN-CVE-2025-37739, GHSA-qc3f-4c25-g23q, ROOT-OS-DEBIAN-12-CVE-2025-37739, ROOT-OS-UBUNTU-2204-CVE-2025-37739, ROOT-OS-UBUNTU-2404-CVE-2025-37739, UBUNTU-CVE-2025-37739

## What is CVE-2025-37739?

CVE-2025-37739 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 1 May 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 avoid out-of-bounds access in f2fs_truncate_inode_blocks()

syzbot reports an UBSAN issue as below:

------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in fs/f2fs/node.h:381:10
index 18446744073709550692 is out of range for type '__le32[5]' (aka 'unsigned int[5]')
CPU: 0 UID: 0 PID: 5318 Comm: syz.0.0 Not tainted 6.14.0-rc3-syzkaller-00060-g6537cfb395f3 #0
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 ubsan_epilogue lib/ubsan.c:231 [inline]
 __ubsan_handle_out_of_bounds+0x121/0x150 lib/ubsan.c:429
 get_nid fs/f2fs/node.h:381 [inline]
 f2fs_truncate_inode_blocks+0xa5e/0xf60 fs/f2fs/node.c:1181
 f2fs_do_truncate_blocks+0x782/0x1030 fs/f2fs/file.c:808
 f2fs_truncate_blocks+0x10d/0x300 fs/f2fs/file.c:836
 f2fs_truncate+0x417/0x720 fs/f2fs/file.c:886
 f2fs_file_write_iter+0x1bdb/0x2550 fs/f2fs/file.c:5093
 aio_write+0x56b/0x7c0 fs/aio.c:1633
 io_submit_one+0x8a7/0x18a0 fs/aio.c:2052
 __do_sys_io_submit fs/aio.c:2111 [inline]
 __se_sys_io_submit+0x171/0x2e0 fs/aio.c:2081
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f238798cde9

index 18446744073709550692 (decimal, unsigned long long)
= 0xfffffffffffffc64 (hexadecimal, unsigned long long)
= -924 (decimal, long long)

In f2fs_truncate_inode_blocks(), UBSAN detects that get_nid() tries to
access .i_nid[-924], it means both offset[0] and level should zero.

The possible case should be in f2fs_do_truncate_blocks(), we try to
truncate inode size to zero, however, dn.ofs_in_node is zero and
dn.node_page is not an inode page, so it fails to truncate inode page,
and then pass zeroed free_from to f2fs_truncate_inode_blocks(), result
in this issue.

	if (dn.ofs_in_node || IS_INODE(dn.node_page)) {
		f2fs_truncate_data_blocks_range(&dn, count);
		free_from += count;
	}

I guess the reason why dn.node_page is not an inode page could be: there
are multiple nat entries share the same node block address, once the node
block address was reused, f2fs_get_node_page() may load a non-inode block.

Let's add a sanity check for such condition to avoid out-of-bounds access
issue.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2025-37739?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-37739?

Apply the vendor's patch.

## Is CVE-2025-37739 being exploited?

There is no known exploitation of CVE-2025-37739 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-37739 and fix it if it is affected.

What it is: CVE-2025-37739 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 1 May 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-2025-37739 in the wild and no public exploit code.

Affected product: Debian Debian 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-2025-37739/ (Markdown: https://insights.sbomify.com/CVE-2025-37739/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-37739
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-37739
- OSV: https://osv.dev/vulnerability/CVE-2025-37739

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-37739/
Summaries are generated and may contain mistakes; the official description above is the record.