# CVE-2026-43067: ext4: handle wraparound when searching for blocks for indirect mapped blocks

> An integer wraparound in ext4 block allocation allows attackers to read or modify data outside intended bounds on indirect-mapped files.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-43067, DEBIAN-CVE-2026-43067, GHSA-845x-q62g-4v8p, UBUNTU-CVE-2026-43067

## What is CVE-2026-43067?

CVE-2026-43067 is a critical vulnerability in Linux kernel, published on 5 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

ext4: handle wraparound when searching for blocks for indirect mapped blocks

Commit 4865c768b563 ("ext4: always allocate blocks only from groups
inode can use") restricts what blocks will be allocated for indirect
block based files to block numbers that fit within 32-bit block
numbers.

However, when using a review bot running on the latest Gemini LLM to
check this commit when backporting into an LTS based kernel, it raised
this concern:

   If ac->ac_g_ex.fe_group is >= ngroups (for instance, if the goal
   group was populated via stream allocation from s_mb_last_groups),
   then start will be >= ngroups.

   Does this allow allocating blocks beyond the 32-bit limit for
   indirect block mapped files? The commit message mentions that
   ext4_mb_scan_groups_linear() takes care to not select unsupported
   groups. However, its loop uses group = *start, and the very first
   iteration will call ext4_mb_scan_group() with this unsupported
   group because next_linear_group() is only called at the end of the
   iteration.

After reviewing the code paths involved and considering the LLM
review, I determined that this can happen when there is a file system
where some files/directories are extent-mapped and others are
indirect-block mapped.  To address this, add a safety clamp in
ext4_mb_scan_groups().

Weakness: CWE-822 (Untrusted Pointer Dereference)

## Which versions are affected by CVE-2026-43067?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43067?

Apply the vendor's patch.

## Is CVE-2026-43067 being exploited?

There is no known exploitation of CVE-2026-43067 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-2026-43067 and fix it if it is affected.

What it is: CVE-2026-43067 is a critical vulnerability in Linux kernel, published on 5 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-43067 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-2026-43067/ (Markdown: https://insights.sbomify.com/CVE-2026-43067/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43067
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43067
- OSV: https://osv.dev/vulnerability/CVE-2026-43067

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43067/
Summaries are generated and may contain mistakes; the official description above is the record.