CVE-2026-53550: CWE-407: Inefficient Algorithmic Complexity in nodeca js-yaml
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.
AI Analysis
Technical Summary
The vulnerability in js-yaml (CVE-2026-53550) arises from inefficient algorithmic complexity (CWE-407) in the handling of merge keys (<<) within lib/loader.js. Specifically, repeating the same alias multiple times in a merge sequence triggers quadratic parse-time behavior relative to input size, causing CPU exhaustion and blocking the Node.js worker/event loop for several seconds with a relatively small payload. This results in a denial of service condition. The issue affects versions prior to 4.2.0 and 3.15.0 and has been addressed in those fixed releases.
Potential Impact
An attacker can cause denial of service by submitting a crafted YAML document that exploits the quadratic CPU consumption during merge-key processing. This can block the Node.js event loop, potentially disrupting applications relying on js-yaml parsing. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
This vulnerability is fixed in js-yaml versions 4.2.0 and 3.15.0. Users should upgrade to at least version 4.2.0 or 3.15.0 to remediate this issue. Patch status is confirmed by the version information in the description. No additional mitigations are specified.
CVE-2026-53550: CWE-407: Inefficient Algorithmic Complexity in nodeca js-yaml
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.
CVSS v3.1
Score 5.3medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in js-yaml (CVE-2026-53550) arises from inefficient algorithmic complexity (CWE-407) in the handling of merge keys (<<) within lib/loader.js. Specifically, repeating the same alias multiple times in a merge sequence triggers quadratic parse-time behavior relative to input size, causing CPU exhaustion and blocking the Node.js worker/event loop for several seconds with a relatively small payload. This results in a denial of service condition. The issue affects versions prior to 4.2.0 and 3.15.0 and has been addressed in those fixed releases.
Potential Impact
An attacker can cause denial of service by submitting a crafted YAML document that exploits the quadratic CPU consumption during merge-key processing. This can block the Node.js event loop, potentially disrupting applications relying on js-yaml parsing. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
This vulnerability is fixed in js-yaml versions 4.2.0 and 3.15.0. Users should upgrade to at least version 4.2.0 or 3.15.0 to remediate this issue. Patch status is confirmed by the version information in the description. No additional mitigations are specified.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-09T18:13:07.263Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a39572aeed863c81e05382e
Added to database: 06/22/2026, 15:39:22 UTC
Last enriched: 06/29/2026, 21:02:23 UTC
Last updated: 08/06/2026, 00:41:14 UTC
Views: 93
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