# Improper rate limiting in Koel

Advisory record · `GHSA-r37h-j483-cjjm`

- **Identifiers:** `GHSA-r37h-j483-cjjm` · `CVE-2021-33563` · `PKSA-929f-gr4s-2fz1`
- **State:** Confirmed
- **Severity:** No CVSS score
- **Critical:** No
- **Weakness (CWE):** [CWE-799](https://cwe.mitre.org/data/definitions/799.html) · [CWE-916](https://cwe.mitre.org/data/definitions/916.html)
- **Tags:** [Weak cryptography or TLS](https://agentprime.io/advisories/tag/weak-crypto.md) · [CWE-799](https://agentprime.io/advisories/tag/cwe-799.md)
- **Published:** 1 Jun 2021
- **Updated:** 2 Dec 2024
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 1 Jun 2021, 21:38 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `phanan/koel` (Packagist): affected `<5.1.4`; fixed in `5.1.4`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Koel versions before 5.1.4 lack login throttling and a password strength policy, and failed login attempts reveal whether a username is valid. An attacker with network access to the login page could use this to make brute-force guessing of passwords easier. Upgrade to Koel 5.1.4 or later, which is the listed fixed version.

Written 4 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

No source has published a CVSS score for this record yet.

- **CISA KEV:** Not listed.
- **EPSS:** 0.0081, the 57th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:28 UTC: First seen by agentprime
- 31 Oct 2026, 14:28 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-r37h-j483-cjjm)

## Sources

- [GitHub Advisory Database: GHSA-r37h-j483-cjjm](https://github.com/advisories/GHSA-r37h-j483-cjjm)
- [OSV: GHSA-r37h-j483-cjjm](https://osv.dev/vulnerability/GHSA-r37h-j483-cjjm)
- <https://nvd.nist.gov/vuln/detail/CVE-2021-33563>
- <https://github.com/koel/koel/releases/tag/v5.1.4>
- <https://huntr.dev/bounties/1-other-koel/koel>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-r37h-j483-cjjm>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-r37h-j483-cjjm/>. Everything for agents: <https://agentprime.io/llms.txt>.