# CVE-2026-6682: FatFs Integer Overflow in FAT32 Volume Mount

> An integer overflow in FatFs allows attackers to trigger unsafe memory operations via crafted FAT32 volumes, potentially leading to code execution or denial of service.

- **Severity:** High 7.6 (`CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Jul 2026
- **Updated:** 1 Jul 2026
- **Also known as:** GHSA-c25x-vcg6-4ccx

## What is CVE-2026-6682?

CVE-2026-6682 is a high-severity vulnerability in ChaN FatFs, published on 1 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In FatFS R0.16 and earlier contains a FAT32 integer overflow bug in mount_volume() where fasize *= fs->n_fats can wrap, leading to attacker-controlled file-size metadata and unsafe read lengths in downstream callers. This maps to CWE-190 (Integer Overflow or Wraparound). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H (7.6, High). Remote delivery is also possible in OTA/update pipelines. The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-6682?

It affects 1 product.


Products: Elm-Chan Fatfs.

## How do I fix CVE-2026-6682?

No fix has been published for CVE-2026-6682 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-6682 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-6682 exists.

## Other vulnerabilities in ChaN FatFs

- [CVE-2026-6687](https://insights.sbomify.com/CVE-2026-6687/): FatFs Stack Buffer Overflow via Uncapped exFAT Label Length (high 7.6)
- [CVE-2026-6688](https://insights.sbomify.com/CVE-2026-6688/): FatFs Buffer Overflow via Unbounded LFN Filename Copy (high 7.6)
- [CVE-2026-6683](https://insights.sbomify.com/CVE-2026-6683/): FatFs Divide-by-Zero in exFAT Sync (medium 4.6)
- [CVE-2026-6684](https://insights.sbomify.com/CVE-2026-6684/): FatFs Infinite Loop in GPT Partition Scan (medium 4.6)
- [CVE-2026-6686](https://insights.sbomify.com/CVE-2026-6686/): FatFs Use of Uninitialized Clusters After Seek Past EOF (medium 4.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-6682 and fix it if it is affected.

What it is: CVE-2026-6682 is a high-severity vulnerability in ChaN FatFs, published on 1 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-6682 exists.

Affected product: ChaN FatFs. 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-2026-6682/ (Markdown: https://insights.sbomify.com/CVE-2026-6682/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-6682
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-6682
- OSV: https://osv.dev/vulnerability/CVE-2026-6682

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-6682/
Summaries are generated and may contain mistakes; the official description above is the record.