Allocation of Resources Without Limits or Throttling Affecting js-yaml package, versions >=3.0.0 <3.15.2>=4.0.0 <4.3.2
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-JS-JSYAML-19496768
- published2 Sept 2026
- disclosed2 Sept 2026
- creditUnknown
Introduced: 2 Sep 2026
NewCVE-2026-84375 (opens in a new tab)How to fix?
Upgrade js-yaml to version 3.15.2, 4.3.2 or higher.
Overview
js-yaml is a human-friendly data serialization language.
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling in the merge key (<<) handling of the loader, where the maxTotalMergeKeys budget does not count empty mappings against its limit. An attacker can consume significant CPU, on the order of O(N*K) for N empty mappings merged K times, with a relatively small document by repeatedly merging a large sequence of empty mappings so the budget counter never increments.
Note: This requires YAML merge processing to be enabled for untrusted YAML, which is the default behavior in versions 3 and 4, but is not the default in version 5.