Answer in brief
CVE-2026-84375 records a High severity (CVSS 7.5) vulnerability in js-yaml: maxTotalMergeKeys does not limit CPU use for empty merge sources. The current sources do not mark it as known exploited. The current feed maps nodeca/js-yaml (generic), nodeca/js-yaml (generic), js-yaml (npm), js-yaml (npm). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps nodeca/js-yaml (generic), nodeca/js-yaml (generic), js-yaml (npm), js-yaml (npm). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| nodeca/js-yamlgeneric | >=3.0.0 <3.15.2 || >=4.0.0 <4.3.2 | 3.15.2, 4.3.2 |
| nodeca/js-yamlgeneric | >=3.0.0 <3.15.2 || >=4.0.0 <4.3.2 || >=5.0.0 <5.4.1 | 3.15.2, 4.3.2, 5.4.1 |
| js-yamlnpm | >=4.0.0,<4.3.2 | 4.3.2 |
| js-yamlnpm | >=3.0.0,<3.15.2 | 3.15.2 |
Published upstream
Sep 1, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 1, 2026
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.
Quoted source text, attributed separately from HOL analysis.