# CVE-2026-74308: ext4: fix kernel BUG in ext4_write_inline_data_end

> A local attacker can trigger a kernel crash in the ext4 filesystem when using the data=journal mount option, causing a denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-74308, DEBIAN-CVE-2026-74308, GHSA-grvr-g5pp-pc9x, UBUNTU-CVE-2026-74308

## What is CVE-2026-74308?

CVE-2026-74308 is a denial of service vulnerability in Linux, published on 15 Aug 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: fix kernel BUG in ext4_write_inline_data_end

When the data=journal mount option is used, the ext4_journalled_write_end()
function incorrectly calls ext4_write_inline_data_end() without checking
if the EXT4_STATE_MAY_INLINE_DATA flag is still set on the inode.

If a previous attempt to convert the inline data to an extent failed (e.g.
due to ENOSPC), the EXT4_STATE_MAY_INLINE_DATA flag is cleared, but
the EXT4_INODE_INLINE_DATA flag remains set. In this scenario, the next
call to ext4_write_begin() will not prepare the inline data xattr for
writing, but ext4_journalled_write_end() will incorrectly attempt to write
to it, triggering a BUG_ON(pos + len > EXT4_I(inode)->i_inline_size) in
ext4_write_inline_data() since i_inline_size was not expanded.

Fix this by ensuring that ext4_journalled_write_end() only calls
ext4_write_inline_data_end() if the EXT4_STATE_MAY_INLINE_DATA flag is
set, mirroring the behavior of ext4_write_end() and ext4_da_write_end().

## Which versions are affected by CVE-2026-74308?


## How do I fix CVE-2026-74308?

Apply the vendor's patch.

## Is CVE-2026-74308 being exploited?

There is no known exploitation of CVE-2026-74308 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74308 and fix it if it is affected.

What it is: CVE-2026-74308 is a denial of service vulnerability in Linux, published on 15 Aug 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-2026-74308 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-2026-74308/ (Markdown: https://insights.sbomify.com/CVE-2026-74308/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74308
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74308
- OSV: https://osv.dev/vulnerability/CVE-2026-74308

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74308/
Summaries are generated and may contain mistakes; the official description above is the record.