# CVE-2026-8236: Concrete CMS is vulnerable to IDOR combined with a missing authentication gate

> Unauthenticated attackers can access internal site structure data via an insecure direct object reference in the file usage endpoint.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 May 2026
- **Updated:** 22 May 2026
- **Also known as:** GHSA-58c8-vvqw-cm7m

## What is CVE-2026-8236?

CVE-2026-8236 is a medium-severity missing authorization vulnerability in Concretecms Concrete Cms, published on 21 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Concrete CMS 9.5.0 and below is vulnerable to IDOR combined with a missing authentication gate. The endpoint /ccm/system/dialogs/file/usage/{fID} accepts an integer file ID in the URL and returns internal site structure data (page IDs, versions, URL paths) to anyone who sends a GET request. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-8236?

2 open source packages ship an affected version, including concrete5/concrete5. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `concrete5/concrete5` | Packagist | All versions | 9.5.1 |
| `concrete5/concrete5` | Packagist | All versions | 9.5.1 |

Products: Concretecms Concrete Cms.

## How do I fix CVE-2026-8236?

Upgrade concrete5/concrete5 to 9.5.1 or later.

## Is CVE-2026-8236 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-8236 exists.

Public exploit code:

- Concrete CMS <9.5.1 - Unauthenticated File-Usage Internal Metadata Disclosure (nuclei): http/cves/2026/CVE-2026-8236.yaml

## Other vulnerabilities in Concretecms Concrete Cms

- [CVE-2023-48648](https://insights.sbomify.com/CVE-2023-48648/): Concrete CMS allows unauthorized access because directories can be created with insecure permissions (critical 9.8)
- [CVE-2022-21829](https://insights.sbomify.com/CVE-2022-21829/): Code injection in concrete CMS (critical 9.8)
- [CVE-2021-22958](https://insights.sbomify.com/CVE-2021-22958/): Server-Side Request Forgery vulnerability in concrete5 (critical 9.8)
- [CVE-2021-40098](https://insights.sbomify.com/CVE-2021-40098/): Path traversal in n/a (critical 9.8)
- [CVE-2026-8134](https://insights.sbomify.com/CVE-2026-8134/): Concrete CMS Vulnerable to Relative Path Traversal (critical 9.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-8236 and fix it if it is affected.

What it is: CVE-2026-8236 is a medium-severity missing authorization vulnerability in Concretecms Concrete Cms, published on 21 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-8236 exists.

Affected packages and fixed versions:
- concrete5/concrete5 (Packagist): affected all versions; fixed in 9.5.1
- concrete5/concrete5 (Packagist): affected all versions; fixed in 9.5.1

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-2026-8236/ (Markdown: https://insights.sbomify.com/CVE-2026-8236/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-8236
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-8236
- OSV: https://osv.dev/vulnerability/CVE-2026-8236

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-8236/
Summaries are generated and may contain mistakes; the official description above is the record.