# CVE-2026-57856: Cockpit CMS Path Traversal via Bucket Name in Bucket File Storage API

> Authenticated low-privileged users can traverse directories to list, upload, and delete files across all buckets in Cockpit CMS.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/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:** 13 Jul 2026
- **Updated:** 14 Jul 2026
- **Also known as:** GHSA-cfx5-q5qm-x936

## What is CVE-2026-57856?

CVE-2026-57856 is a high-severity path traversal vulnerability in Cockpit CMS, published on 13 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Cockpit CMS contains a path traversal vulnerability in the Bucket file storage API (/system/buckets/api). The api() method in modules/System/Controller/Buckets.php sanitizes the bucket name with preg_replace('/[^a-zA-Z0-9-_\\.]/','', $bucket), which permits '..' and '../' sequences. The sanitized value is interpolated into a Flysystem path as uploads://buckets/{bucket}. Flysystem's WhitespacePathNormalizer resolves 'buckets/..' to the empty string (the uploads storage root) without raising PathTraversalDetected because the '..' has a preceding component to consume. An authenticated low-privileged user can send a crafted request with a '../' bucket name to list, upload, and delete files across all buckets, including those belonging to other users or roles

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-57856?


## How do I fix CVE-2026-57856?

No fix has been published for CVE-2026-57856 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-57856 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-57856 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-57856 and fix it if it is affected.

What it is: CVE-2026-57856 is a high-severity path traversal vulnerability in Cockpit CMS, published on 13 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-57856 exists.

Affected product: Cockpit 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-2026-57856/ (Markdown: https://insights.sbomify.com/CVE-2026-57856/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-57856
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-57856
- OSV: https://osv.dev/vulnerability/CVE-2026-57856

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-57856/
Summaries are generated and may contain mistakes; the official description above is the record.