# CVE-2021-40102: Deserialization in n/a

> Attackers can delete arbitrary files in Concrete CMS via PHAR deserialization in the is_dir function, potentially compromising data integrity.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Sep 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-jgcw-5vw9-7w3c

## What is CVE-2021-40102?

CVE-2021-40102 is a critical unsafe deserialization vulnerability in Concretecms Concrete Cms, published on 24 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in Concrete CMS through 8.5.5. Arbitrary File deletion can occur via PHAR deserialization in is_dir (PHP Object Injection associated with the __wakeup magic method).

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2021-40102?

It affects 1 product.


Products: Concretecms Concrete Cms.

## How do I fix CVE-2021-40102?

No fix has been published for CVE-2021-40102 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-40102 being exploited?

There is no known exploitation of CVE-2021-40102 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-2021-40102 and fix it if it is affected.

What it is: CVE-2021-40102 is a critical unsafe deserialization vulnerability in Concretecms Concrete Cms, published on 24 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-40102 in the wild and no public exploit code.

Affected product: Concretecms Concrete 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-2021-40102/ (Markdown: https://insights.sbomify.com/CVE-2021-40102/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-40102
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-40102
- OSV: https://osv.dev/vulnerability/CVE-2021-40102

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-40102/
Summaries are generated and may contain mistakes; the official description above is the record.