# CVE-2026-3452: Concrete CMS below 9.4.8 is vulnerable to stored deserialization leading to RCE in the Express Entry List block.

> An authenticated administrator can achieve remote code execution in Concrete CMS by injecting serialized PHP objects into the Express Entry List block configuration.

- **Severity:** High 8.9 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Mar 2026
- **Updated:** 4 Mar 2026
- **Also known as:** GHSA-gj26-w59c-29mf

## What is CVE-2026-3452?

CVE-2026-3452 is a high-severity unsafe deserialization vulnerability in Concretecms Concrete Cms, published on 4 Mar 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

Concrete CMS below version 9.4.8 is vulnerable to Remote Code Execution by stored PHP object injection into the Express Entry List block via the columns parameter. An authenticated administrator can store attacker-controlled serialized data in block configuration fields that are later passed to unserialize() without class restrictions or integrity checks. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 8.9 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H. Thanks YJK ( @YJK0805 https://hackerone.com/yjk0805 ) of  ZUSO ART https://zuso.ai/  for reporting.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-3452?

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 | 9.4.8 |
| `concrete5/concrete5` | Packagist | All versions | 9.4.8 |

Products: Concretecms Concrete Cms.

## How do I fix CVE-2026-3452?

Upgrade concrete5/concrete5 to 9.4.8 or later.

## Is CVE-2026-3452 being exploited?

There is no known exploitation of CVE-2026-3452 in the wild and no public exploit code.

## 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-2026-3452 and fix it if it is affected.

What it is: CVE-2026-3452 is a high-severity unsafe deserialization vulnerability in Concretecms Concrete Cms, published on 4 Mar 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-3452 in the wild and no public exploit code.

Affected packages and fixed versions:
- concrete5/concrete5 (Packagist): affected all versions; fixed in 9.4.8
- concrete5/concrete5 (Packagist): affected all versions; fixed in 9.4.8

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-2026-3452/ (Markdown: https://insights.sbomify.com/CVE-2026-3452/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3452
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3452
- OSV: https://osv.dev/vulnerability/CVE-2026-3452

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3452/
Summaries are generated and may contain mistakes; the official description above is the record.