Resource exhaustion in Nodeca Js-Yaml

CVE-2026-84375

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.

Vulnerability class: DoS (Denial of Service)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.005 (44.3th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 44.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-84375: held from 0.004 to 0.005.

EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.002

Affected products

  • Nodeca Js-Yaml — versions >= 3.0.0, < 3.15.2, >= 4.0.0, < 4.3.2, >= 5.0.0, < 5.4.1

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-84375?
CVE-2026-84375 is a high-severity vulnerability in Nodeca Js-Yaml, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-09-01.
How severe is CVE-2026-84375?
High severity. CVSS v3 base score is 7.5 out of 10.