# CVE-2021-3987: Improper Access Control in janeczku/calibre-web

> Users without public shelf permissions can create public shelves due to missing authorization checks in Calibre Web.

- **Severity:** Medium 5.4 (`CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Nov 2024
- **Updated:** 15 Nov 2024
- **Also known as:** GHSA-fj5v-w2jp-wqvj, PYSEC-2026-1229

## What is CVE-2021-3987?

CVE-2021-3987 is a medium-severity missing authorization vulnerability in janeczku/calibre-web, published on 15 Nov 2024. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

An improper access control vulnerability exists in janeczku/calibre-web. The affected version allows users without public shelf permissions to create public shelves. The vulnerability is due to the `create_shelf` method in `shelf.py` not verifying if the user has the necessary permissions to create a public shelf. This issue can lead to unauthorized actions being performed by users.

Weakness: CWE-862 (Missing Authorization), CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2021-3987?

3 open source packages ship an affected version, including calibreweb. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `calibreweb` | PyPI | All versions | 0.6.15 |
| `calibreweb` | PyPI | All versions | 0.6.15 |
| `calibreweb` | PyPI | All versions | 0.6.15 |

Products: Janeczku Calibre-Web.

## How do I fix CVE-2021-3987?

Upgrade calibreweb to 0.6.15 or later.

## Is CVE-2021-3987 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-3987 exists.

## Other vulnerabilities in janeczku/calibre-web

- [CVE-2022-30765](https://insights.sbomify.com/CVE-2022-30765/): SQL injection in calibreweb (critical 9.8)
- [CVE-2020-12627](https://insights.sbomify.com/CVE-2020-12627/): Hardcoded credentials in n/a (critical 9.8)
- [CVE-2022-0990](https://insights.sbomify.com/CVE-2022-0990/): Server-Side Request Forgery (SSRF) in janeczku/calibre-web (critical 9.3)
- [CVE-2022-0767](https://insights.sbomify.com/CVE-2022-0767/): Server-Side Request Forgery (SSRF) in janeczku/calibre-web (critical 9.1)
- [CVE-2022-0939](https://insights.sbomify.com/CVE-2022-0939/): Server-Side Request Forgery (SSRF) in janeczku/calibre-web (critical 9.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3987 and fix it if it is affected.

What it is: CVE-2021-3987 is a medium-severity missing authorization vulnerability in janeczku/calibre-web, published on 15 Nov 2024. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-3987 exists.

Affected packages and fixed versions:
- calibreweb (PyPI): affected all versions; fixed in 0.6.15
- calibreweb (PyPI): affected all versions; fixed in 0.6.15
- calibreweb (PyPI): affected all versions; fixed in 0.6.15

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-2021-3987/ (Markdown: https://insights.sbomify.com/CVE-2021-3987/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3987
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3987
- OSV: https://osv.dev/vulnerability/CVE-2021-3987

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3987/
Summaries are generated and may contain mistakes; the official description above is the record.