High
node-js-yaml — security advisory
js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 until 3.15.2, 4.3.2, and 5.4.1, maxTotalMergeKeys in lib/js-yaml/loader.js and lib/loader.js does not count empty mapping sources while processing the merge key <<. An attacker can alias a large sequence of empty mappings into many merge targets, causing O(N * K) processing while totalMergeKeys remains unchanged and the configured resource limit is never reached. A relatively small YAML document can therefore cause prolonged CPU consumption in applications that parse untrusted YAML, and merge processing is enabled by default on these release lines. In v3 & v4, merge is enabled by default so the severity score is higher. This issue is fixed in versions 3.15.2, 4.3.2, and 5.4.1.
- 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-2026-84375
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:22 UTC · Revision 1
Source evidence
js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 until 3.15.2, 4.3.2, and 5.4.1, maxTotalMergeKeys in lib/js-yaml/loader.js and lib/loader.js does not count empty mapping sources while processing the merge key <<. An attacker can alias a large sequence of empty mappings into many merge targets, causing O(N * K) processing while totalMergeKeys remains unchanged and the configured resource limit is never reached. A relatively small YAML document can therefore cause prolonged CPU consumption in applications that parse untrusted YAML, and merge processing is enabled by default on these release lines. In v3 & v4, merge is enabled by default so the severity score is higher. This issue is fixed in versions 3.15.2, 4.3.2, and 5.4.1.
osv:UBUNTU-CVE-2026-84375
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": "6b2311a4cb0f1cd375f1c8618bbe534d8a578f93ee507afff51fe0f2e4d49579",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-84375",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-84375",
"summary": "js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 until 3.15.2, 4.3.2, and 5.4.1, maxTotalMergeKeys in lib/js-yaml/loader.js and lib/loader.js does not count empty mapping sources while processing the merge key <<. An attacker can alias a large sequence of empty mappings into many merge targets, causing O(N * K) processing while totalMergeKeys remains unchanged and the configured resource limit is never reached. A relatively small YAML document can therefore cause prolonged CPU consumption in applications that parse untrusted YAML, and merge processing is enabled by default on these release lines. In v3 & v4, merge is enabled by default so the severity score is higher. This issue is fixed in versions 3.15.2, 4.3.2, and 5.4.1.",
"evidence": "osv:UBUNTU-CVE-2026-84375",
"products": [
{
"name": {
"value": "node-js-yaml",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.9.1+dfsg-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.10.0+dfsg-1",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "node-js-yaml",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.13.1+dfsg-2",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "node-js-yaml",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.14.1+dfsg+~3.12.6-2",
"evidence": "/affected/2/versions"
},
{
"value": "4.1.0+dfsg+~4.0.5-4ubuntu1",
"evidence": "/affected/2/versions"
},
{
"value": "4.1.0+dfsg+~4.0.5-5",
"evidence": "/affected/2/versions"
},
{
"value": "4.1.0+dfsg+~4.0.5-6",
"evidence": "/affected/2/versions"
}
]
},
{
"name": {
"value": "node-js-yaml",
"evidence": "/affected/3/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "4.1.0+dfsg+~4.0.5-7",
"evidence": "/affected/3/versions"
}
]
},
{
"name": {
"value": "node-js-yaml",
"evidence": "/affected/4/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "4.1.1+dfsg+~4.0.9-1",
"evidence": "/affected/4/versions"
},
{
"value": "4.2.0+~4.0.9-1",
"evidence": "/affected/4/versions"
},
{
"value": "4.2.0+~4.0.9-2",
"evidence": "/affected/4/versions"
}
]
},
{
"name": {
"value": "node-js-yaml",
"evidence": "/affected/5/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "4.1.0+dfsg+~4.0.5-7",
"evidence": "/affected/5/versions"
},
{
"value": "4.1.1+dfsg+~4.0.9-1",
"evidence": "/affected/5/versions"
}
]
}
],
"severity": "high",
"structured": {
"id": "UBUNTU-CVE-2026-84375",
"aliases": [
"UBUNTU-CVE-2026-84375"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "node-js-yaml",
"purl": "pkg:deb/ubuntu/node-js-yaml?arch=source&distro=bionic",
"ecosystem": "Ubuntu:18.04:LTS"
},
"versions": [
"3.9.1+dfsg-1",
"3.10.0+dfsg-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-84375.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-js-yaml",
"binary_version": "3.10.0+dfsg-1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "node-js-yaml",
"purl": "pkg:deb/ubuntu/node-js-yaml?arch=source&distro=focal",
"ecosystem": "Ubuntu:20.04:LTS"
},
"versions": [
"3.13.1+dfsg-2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-84375.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-js-yaml",
"binary_version": "3.13.1+dfsg-2"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "node-js-yaml",
"purl": "pkg:deb/ubuntu/node-js-yaml?arch=source&distro=jammy",
"ecosystem": "Ubuntu:22.04:LTS"
},
"versions": [
"3.14.1+dfsg+~3.12.6-2",
"4.1.0+dfsg+~4.0.5-4ubuntu1",
"4.1.0+dfsg+~4.0.5-5",
"4.1.0+dfsg+~4.0.5-6"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-84375.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-js-yaml",
"binary_version": "4.1.0+dfsg+~4.0.5-6"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
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],
"package": {
"name": "node-js-yaml",
"purl": "pkg:deb/ubuntu/node-js-yaml?arch=source&distro=noble",
"ecosystem": "Ubuntu:24.04:LTS"
},
"versions": [
"4.1.0+dfsg+~4.0.5-7"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-84375.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-js-yaml",
"binary_version": "4.1.0+dfsg+~4.0.5-7"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
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],
"package": {
"name": "node-js-yaml",
"purl": "pkg:deb/ubuntu/node-js-yaml?arch=source&distro=stonking",
"ecosystem": "Ubuntu:26.10"
},
"versions": [
"4.1.1+dfsg+~4.0.9-1",
"4.2.0+~4.0.9-1",
"4.2.0+~4.0.9-2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-84375.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-js-yaml",
"binary_version": "4.2.0+~4.0.9-2"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "node-js-yaml",
"purl": "pkg:deb/ubuntu/node-js-yaml?arch=source&distro=resolute",
"ecosystem": "Ubuntu:26.04:LTS"
},
"versions": [
"4.1.0+dfsg+~4.0.5-7",
"4.1.1+dfsg+~4.0.9-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-84375.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "node-js-yaml",
"binary_version": "4.1.1+dfsg+~4.0.9-1"
}
]
}
}
],
"modified": "2026-10-17T13:01:12.298481867Z",
"provider": "osv",
"upstream": [
"CVE-2026-84375"
],
"references": [
"https://ubuntu.com/security/CVE-2026-84375",
"https://www.cve.org/CVERecord?id=CVE-2026-84375",
"https://github.com/nodeca/js-yaml/security/advisories/GHSA-2883-xcg3-v3hh",
"https://github.com/nodeca/js-yaml/pull/797"
]
},
"related_cves": [
{
"value": "CVE-2026-84375",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 361224,
"published_at": "2026-09-01T22:17:00+00:00"
}