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CVE-2026-53550

27
FAUCET Score

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.

First published: Jun 22, 2026Last modified: Jun 29, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 3.15.0CPE matchmatch criteria
cpe:2.3:a:nodeca:js-yaml:*:*:*:*:*:node.js:*:*
>= 4.0.0, < 4.2.0CPE matchmatch criteria
cpe:2.3:a:nodeca:js-yaml:*:*:*:*:*:node.js:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
LOW
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.38%
Probability of exploitation in next 30 days
EPSS Percentile
30.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0038 is in the 19th percentile among its peer group of 23,703 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

npmpatch availablevia ghsa
Product: js-yamlFixed in: 4.2.0
npmpatch availablevia ghsa
Product: js-yamlFixed in: 3.15.0
github_advisoryworkaround availablevia nvd_reference
View patch

Vendor Advisories (1)

npmGHSA-h67p-54hq-rp68medium

JS-YAML: Quadratic-complexity DoS in merge key handling via repeated aliases

Jun 15, 2026

References

github.com / nodeca/js-yaml/security/advisories/GHSA-h67p-54hq-rp68
ExploitMitigationVendor Advisory