# CVE-2026-82450: BookStack before 26.05.4 Remote Code Execution via Book Cover

> Attackers with import permissions can upload malicious PHP files as book covers to achieve remote code execution on BookStack instances.

- **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:** 29 Aug 2026
- **Updated:** 8 Oct 2026
- **Also known as:** GHSA-jgmr-x24h-q8jj

## What is CVE-2026-82450?

CVE-2026-82450 is a high-severity vulnerability in bookstackapp bookstack, published on 29 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

BookStack before 26.05.4 contains a remote code execution vulnerability in the portable ZIP import functionality that allows users with Import Content and Create Books permissions to upload a PHP polyglot file as a book cover. Attackers can bypass image extension validation by embedding a PHP file with a .php filename in the ZIP archive, which is stored in the public web root and executed by unauthenticated requests.

Weakness: CWE-434 (Unrestricted Upload of File with Dangerous Type)

## Which versions are affected by CVE-2026-82450?


## How do I fix CVE-2026-82450?

No fix has been published for CVE-2026-82450 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-82450 being exploited?

There is no known exploitation of CVE-2026-82450 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-82450 and fix it if it is affected.

What it is: CVE-2026-82450 is a high-severity vulnerability in bookstackapp bookstack, published on 29 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-82450 in the wild and no public exploit code.

Affected product: bookstackapp bookstack. 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-2026-82450/ (Markdown: https://insights.sbomify.com/CVE-2026-82450/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-82450
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-82450
- OSV: https://osv.dev/vulnerability/CVE-2026-82450

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-82450/
Summaries are generated and may contain mistakes; the official description above is the record.