# CVE-2026-31452: ext4: convert inline data to extents when truncate exceeds inline size

> A local attacker can trigger a kernel crash in the ext4 filesystem by truncating a file with inline data to a size exceeding inline capacity.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 22 Apr 2026
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-83204, BELL-CVE-2026-31452, DEBIAN-CVE-2026-31452, GHSA-g495-4jqx-cp59, ROOT-OS-DEBIAN-11-CVE-2026-31452, ROOT-OS-DEBIAN-12-CVE-2026-31452, ROOT-OS-DEBIAN-13-CVE-2026-31452, ROOT-OS-UBUNTU-2204-CVE-2026-31452, ROOT-OS-UBUNTU-2404-CVE-2026-31452, UBUNTU-CVE-2026-31452

## What is CVE-2026-31452?

CVE-2026-31452 is a high-severity denial of service vulnerability in Linux kernel, published on 22 Apr 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:

ext4: convert inline data to extents when truncate exceeds inline size

Add a check in ext4_setattr() to convert files from inline data storage
to extent-based storage when truncate() grows the file size beyond the
inline capacity. This prevents the filesystem from entering an
inconsistent state where the inline data flag is set but the file size
exceeds what can be stored inline.

Without this fix, the following sequence causes a kernel BUG_ON():

1. Mount filesystem with inode that has inline flag set and small size
2. truncate(file, 50MB) - grows size but inline flag remains set
3. sendfile() attempts to write data
4. ext4_write_inline_data() hits BUG_ON(write_size > inline_capacity)

The crash occurs because ext4_write_inline_data() expects inline storage
to accommodate the write, but the actual inline capacity (~60 bytes for
i_block + ~96 bytes for xattrs) is far smaller than the file size and
write request.

The fix checks if the new size from setattr exceeds the inode's actual
inline capacity (EXT4_I(inode)->i_inline_size) and converts the file to
extent-based storage before proceeding with the size change.

This addresses the root cause by ensuring the inline data flag and file
size remain consistent during truncate operations.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-31452?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31452?

Apply the vendor's patch.

## Is CVE-2026-31452 being exploited?

There is no known exploitation of CVE-2026-31452 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-2026-31452 and fix it if it is affected.

What it is: CVE-2026-31452 is a high-severity denial of service vulnerability in Linux kernel, published on 22 Apr 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-2026-31452 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-2026-31452/ (Markdown: https://insights.sbomify.com/CVE-2026-31452/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31452
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31452
- OSV: https://osv.dev/vulnerability/CVE-2026-31452

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31452/
Summaries are generated and may contain mistakes; the official description above is the record.