Medium
node-js-yaml — security advisory
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.
- Products
- node-js-yaml
- Affected versions
- 3.10.0+dfsg-1, 3.13.1+dfsg-2, 3.14.1+dfsg+~3.12.6-2, 3.9.1+dfsg-1, 4.1.0+dfsg+~4.0.5-4ubuntu1, 4.1.0+dfsg+~4.0.5-5, 4.1.0+dfsg+~4.0.5-6, 4.1.0+dfsg+~4.0.5-7, 4.1.1+dfsg+~4.0.9-1, 4.2.0+~4.0.9-1, 4.2.0+~4.0.9-2
- Fixed versions
- Not specified
- CVEs
- CVE-2026-53550
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 01:06 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-53550
node-js-yaml
Fixed versions: Not specified
node-js-yaml
Fixed versions: Not specified
node-js-yaml
Fixed versions: Not specified
node-js-yaml
Fixed versions: Not specified
node-js-yaml
Fixed versions: Not specified
node-js-yaml
Fixed versions: Not specified
node-js-yaml
Fixed versions: Not specified
Complete source record
{
"id": "37f3eeccc3e321432806ca1137ccf1c5bda1985e2a4ca857117d32f063b1c53f",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-53550",
"method": "structured",
"payload": {
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"title": "UBUNTU-CVE-2026-53550",
"summary": "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.",
"evidence": "osv:UBUNTU-CVE-2026-53550",
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"severity": "medium",
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"aliases": [
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"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
},
{
"type": "Ubuntu",
"score": "medium"
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"affected": [
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"modified": "2026-10-17T12:56:30.229040265Z",
"provider": "osv",
"upstream": [
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]
},
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"source_id": "core-osv",
"document_id": 355746,
"published_at": "2026-06-22T16:16:00+00:00"
}