# CVE-2021-3851: Open Redirect in firefly-iii/firefly-iii

> An attacker can redirect users to malicious sites via Firefly III, potentially facilitating phishing attacks.

- **Severity:** Medium 5.0 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 19 Oct 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-5fvx-5p2r-4mvp

## What is CVE-2021-3851?

CVE-2021-3851 is a medium-severity vulnerability in firefly-iii/firefly-iii, published on 19 Oct 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

firefly-iii is vulnerable to URL Redirection to Untrusted Site

Weakness: CWE-601 (URL Redirection to Untrusted Site)

## Which versions are affected by CVE-2021-3851?

2 open source packages ship an affected version, including grumpydictator/firefly-iii. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `grumpydictator/firefly-iii` | Packagist | All versions | 5.6.2 |
| `grumpydictator/firefly-iii` | Packagist | All versions | 5.6.2 |

Products: Firefly-Iii Firefly Iii.

## How do I fix CVE-2021-3851?

Upgrade grumpydictator/firefly-iii to 5.6.2 or later.

## Is CVE-2021-3851 being exploited?

There is no known exploitation of CVE-2021-3851 in the wild and no public exploit code.

## Other vulnerabilities in firefly-iii/firefly-iii

- [CVE-2023-0298](https://insights.sbomify.com/CVE-2023-0298/): Incorrect Authorization in firefly-iii/firefly-iii (medium 6.5)
- [CVE-2021-3728](https://insights.sbomify.com/CVE-2021-3728/): Cross-Site Request Forgery (CSRF) in firefly-iii/firefly-iii (medium 6.5)
- [CVE-2021-3730](https://insights.sbomify.com/CVE-2021-3730/): Cross-Site Request Forgery (CSRF) in firefly-iii/firefly-iii (medium 6.5)
- [CVE-2021-3846](https://insights.sbomify.com/CVE-2021-3846/): Unrestricted Upload of File with Dangerous Type in firefly-iii/firefly-iii (medium 6.3)
- [CVE-2024-22075](https://insights.sbomify.com/CVE-2024-22075/): Firefly III allows webhooks HTML Injection. (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3851 and fix it if it is affected.

What it is: CVE-2021-3851 is a medium-severity vulnerability in firefly-iii/firefly-iii, published on 19 Oct 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-3851 in the wild and no public exploit code.

Affected packages and fixed versions:
- grumpydictator/firefly-iii (Packagist): affected all versions; fixed in 5.6.2
- grumpydictator/firefly-iii (Packagist): affected all versions; fixed in 5.6.2

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-2021-3851/ (Markdown: https://insights.sbomify.com/CVE-2021-3851/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3851
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3851
- OSV: https://osv.dev/vulnerability/CVE-2021-3851

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3851/
Summaries are generated and may contain mistakes; the official description above is the record.