# CVE-2026-53550: node-js-yaml: js-yaml is a JavaScript YAML parser and dumper

CVE-2026-53550 is fixed in 3 products on 1 platform, first by DEBIAN-CVE-2026-53550, released June 27, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-53550
- Priority: Routine
- CVSS: 5.3 (medium)
- EPSS: 0.0042
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 22, 2026

## Description

js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0 and 3.15.0, a crafted YAML document can trigger algorithmic CPU exhaustion in js-yaml merge-key processing (<<) by repeating the same alias many times in a merge sequence. This causes quadratic parse-time behavior relative to input size and can block a Node.js worker/event loop for seconds with a relatively small payload (tens of KB), resulting in denial of service. The issue is in merge handling inside lib/loader.js. This vulnerability is fixed in 4.2.0 and 3.15.0.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | agama-web-ui opensuse-leap 16.0 | 17+673.b97ba64d6-160000.12.1 | [OPENSUSE-SU-2026:21448-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21448-1.md) | Jul 27, 2026 |
| Linux | node-js-yaml Debian 14 | 4.2.0+~4.0.9-1 | [DEBIAN-CVE-2026-53550](https://patchblox.com/security/data/fix/linux/debian-cve-2026-53550.md) | Jun 27, 2026 |
| Linux | python-pytest-html opensuse-leap 16.0 | 4.1.1-bp160.3.1 | [OPENSUSE-SU-2026:21176-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21176-1.md) | Jun 30, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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