# CVE-2026-84800: Craft CMS 5.0.0-RC1 before 5.10.11 File Overwrite via assets/replace-file

> An authenticated low-privilege user can overwrite peer asset files in shared folders due to missing permission checks in Craft CMS.

- **Severity:** High 7.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Sep 2026
- **Updated:** 2 Sep 2026
- **Also known as:** GHSA-329j-cx85-8r56, GHSA-gr8m-2p6r-xr29

## What is CVE-2026-84800?

CVE-2026-84800 is a high-severity missing authorization vulnerability in craftcms cms, published on 2 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Craft CMS versions >= 5.0.0-RC1 and < 5.10.11 contain a missing authorization vulnerability in AssetsController::actionReplaceFile. When a request supplies sourceAssetId and targetFilename but omits assetId, the target asset is resolved by folder and filename after the permission checks execute, so the replacePeerFiles permission is never enforced. An authenticated low-privilege author with only the replaceFiles permission on a shared folder can overwrite the content of a peer's asset file (located in the same folder) with attacker-controlled bytes. Fixed in 5.10.11.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-84800?


## How do I fix CVE-2026-84800?

No fix has been published for CVE-2026-84800 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-84800 being exploited?

There is no known exploitation of CVE-2026-84800 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-84800 and fix it if it is affected.

What it is: CVE-2026-84800 is a high-severity missing authorization vulnerability in craftcms cms, published on 2 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-84800 in the wild and no public exploit code.

Affected product: craftcms cms. 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-2026-84800/ (Markdown: https://insights.sbomify.com/CVE-2026-84800/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-84800
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-84800
- OSV: https://osv.dev/vulnerability/CVE-2026-84800

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-84800/
Summaries are generated and may contain mistakes; the official description above is the record.