# js-yaml: YAML merge-key chains can force quadratic CPU consumption

Advisory record · `GHSA-52cp-r559-cp3m`

- **Identifiers:** `GHSA-52cp-r559-cp3m` · `CVE-2026-59869`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-400](https://cwe.mitre.org/data/definitions/400.html) · [CWE-407](https://cwe.mitre.org/data/definitions/407.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 20 Jul 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 20 Jul 2026, 21:19 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `js-yaml` (npm): affected `>=3.0.0, <3.15.0 || >=4.0.0, <4.3.0`; fixed in `3.15.0`, `4.3.0`

## 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

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0059, the 48th percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 20 Jul 2026. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-52cp-r559-cp3m](https://github.com/advisories/GHSA-52cp-r559-cp3m)
- [OSV: GHSA-52cp-r559-cp3m](https://osv.dev/vulnerability/GHSA-52cp-r559-cp3m)
- <https://github.com/nodeca/js-yaml/security/advisories/GHSA-52cp-r559-cp3m>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-59869>
- <https://github.com/nodeca/js-yaml/commit/24f13e79ee1343a7e30bd6f6c9d9cdbf0ac9b2b7>
- <https://github.com/nodeca/js-yaml/commit/59423c6f8cdc78742ac00e25a4dd39ef16b702e4>
- <https://github.com/nodeca/js-yaml>
- <https://github.com/nodeca/js-yaml/releases/tag/3.15.0>
- <https://github.com/nodeca/js-yaml/releases/tag/4.3.0>

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-52cp-r559-cp3m>, 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-52cp-r559-cp3m/>. Everything for agents: <https://agentprime.io/llms.txt>.