# CVE-2026-23235: f2fs: fix out-of-bounds access in sysfs attribute read/write

> An out-of-bounds memory access in the Linux kernel f2fs sysfs interface allows attackers to cause memory corruption, potentially leading to code execution or system crashes.

- **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:** 4 Mar 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-23235, DEBIAN-CVE-2026-23235, GHSA-39w6-g297-pmf5, ROOT-OS-DEBIAN-11-CVE-2026-23235, ROOT-OS-DEBIAN-12-CVE-2026-23235, ROOT-OS-DEBIAN-13-CVE-2026-23235, ROOT-OS-UBUNTU-2204-CVE-2026-23235, ROOT-OS-UBUNTU-2404-CVE-2026-23235, UBUNTU-CVE-2026-23235

## What is CVE-2026-23235?

CVE-2026-23235 is a high-severity memory corruption vulnerability in Linux kernel, published on 4 Mar 2026. 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 out-of-bounds access in sysfs attribute read/write

Some f2fs sysfs attributes suffer from out-of-bounds memory access and
incorrect handling of integer values whose size is not 4 bytes.

For example:
vm:~# echo 65537 > /sys/fs/f2fs/vde/carve_out
vm:~# cat /sys/fs/f2fs/vde/carve_out
65537
vm:~# echo 4294967297 > /sys/fs/f2fs/vde/atgc_age_threshold
vm:~# cat /sys/fs/f2fs/vde/atgc_age_threshold
1

carve_out maps to {struct f2fs_sb_info}->carve_out, which is a 8-bit
integer. However, the sysfs interface allows setting it to a value
larger than 255, resulting in an out-of-range update.

atgc_age_threshold maps to {struct atgc_management}->age_threshold,
which is a 64-bit integer, but its sysfs interface cannot correctly set
values larger than UINT_MAX.

The root causes are:
1. __sbi_store() treats all default values as unsigned int, which
prevents updating integers larger than 4 bytes and causes out-of-bounds
writes for integers smaller than 4 bytes.

2. f2fs_sbi_show() also assumes all default values are unsigned int,
leading to out-of-bounds reads and incorrect access to integers larger
than 4 bytes.

This patch introduces {struct f2fs_attr}->size to record the actual size
of the integer associated with each sysfs attribute. With this
information, sysfs read and write operations can correctly access and
update values according to their real data size, avoiding memory
corruption and truncation.

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

## Which versions are affected by CVE-2026-23235?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23235?

Apply the vendor's patch.

## Is CVE-2026-23235 being exploited?

There is no known exploitation of CVE-2026-23235 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23235 and fix it if it is affected.

What it is: CVE-2026-23235 is a high-severity memory corruption vulnerability in Linux kernel, published on 4 Mar 2026. 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-2026-23235 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-23235/ (Markdown: https://insights.sbomify.com/CVE-2026-23235/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23235
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23235
- OSV: https://osv.dev/vulnerability/CVE-2026-23235

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23235/
Summaries are generated and may contain mistakes; the official description above is the record.