# CVE-2020-5256: Remote Code Execution Through Image Uploads in BookStack

> Attackers can upload PHP files via image functions to execute remote code on the host system, affecting BookStack users.

- **Severity:** High 7.9 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 9 Mar 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-g9rq-x4fj-f5hx

## What is CVE-2020-5256?

CVE-2020-5256 is a high-severity vulnerability in BookStackApp BookStack, published on 9 Mar 2020. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

BookStack before version 0.25.5 has a vulnerability where a user could upload PHP files through image upload functions, which would allow them to execute code on the host system remotely. They would then have the permissions of the PHP process. This most impacts scenarios where non-trusted users are given permission to upload images in any area of the application. The issue was addressed in a series of patches in versions 0.25.3, 0.25.4 and 0.25.5. Users should upgrade to at least v0.25.5 to avoid this vulnerability.

Weakness: CWE-434 (Unrestricted Upload of File with Dangerous Type), CWE-95 (Improper Neutralization of Directives in Dynamically Evaluated Code)

## Which versions are affected by CVE-2020-5256?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ssddanbrown/bookstack` | Packagist | All versions | 0.25.5 |
| `ssddanbrown/bookstack` | Packagist | All versions | 0.25.5 |

Products: Bookstackapp Bookstack.

## How do I fix CVE-2020-5256?

Upgrade ssddanbrown/bookstack to 0.25.5 or later.

## Is CVE-2020-5256 being exploited?

There is no known exploitation of CVE-2020-5256 in the wild and no public exploit code.

## Other vulnerabilities in BookStackApp BookStack

- [CVE-2020-26210](https://insights.sbomify.com/CVE-2020-26210/): Cross-Site Scripting in BookStack (high 7.7)
- [CVE-2020-26211](https://insights.sbomify.com/CVE-2020-26211/): Cross-Site Scripting in BookStack (high 7.7)
- [CVE-2022-0877](https://insights.sbomify.com/CVE-2022-0877/): Cross-site Scripting (XSS) - Stored in bookstackapp/bookstack (high 7.6)
- [CVE-2021-3915](https://insights.sbomify.com/CVE-2021-3915/): Unrestricted Upload of File with Dangerous Type in bookstackapp/bookstack (high 7.6)
- [CVE-2023-6199](https://insights.sbomify.com/CVE-2023-6199/): Book Stack v23.10.2 - LFR via Blind SSRF (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-5256 and fix it if it is affected.

What it is: CVE-2020-5256 is a high-severity vulnerability in BookStackApp BookStack, published on 9 Mar 2020. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2020-5256 in the wild and no public exploit code.

Affected packages and fixed versions:
- ssddanbrown/bookstack (Packagist): affected all versions; fixed in 0.25.5
- ssddanbrown/bookstack (Packagist): affected all versions; fixed in 0.25.5

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-2020-5256/ (Markdown: https://insights.sbomify.com/CVE-2020-5256/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-5256
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-5256
- OSV: https://osv.dev/vulnerability/CVE-2020-5256

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-5256/
Summaries are generated and may contain mistakes; the official description above is the record.