js-yaml: maxTotalMergeKeys does not limit CPU use for empty merge sources

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-84375
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-01 22:17:19 UTC
Updated2026-09-01 22:17:19 UTC
Descriptionjs-yaml is a JavaScript YAML parser and dumper. From 3.0.0 until 3.15.2 and 4.3.2, 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. This issue is fixed in versions 3.15.2 and 4.3.2.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

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

Problem Types: CWE-400 | CWE-407 | CWE-400 CWE-400: Uncontrolled Resource Consumption | CWE-407 CWE-407: Inefficient Algorithmic Complexity

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Nodeca Js-yaml affected >= 3.0.0, < 3.15.2 Not specified
CNA Nodeca Js-yaml affected >= 4.0.0, < 4.3.2 Not specified

References

ReferenceSourceLinkTags
github.com/nodeca/js-yaml/commit/d90b6612a5a84385bdcb556c44578eac76dc0f6b [email protected] github.com
github.com/nodeca/js-yaml/commit/6a8e05f9a485188ed730ac81e81ae221352ef480 [email protected] github.com
github.com/nodeca/js-yaml/pull/797 [email protected] github.com
github.com/nodeca/js-yaml/security/advisories/GHSA-2883-xcg3-v3hh [email protected] github.com
github.com/nodeca/js-yaml/releases/tag/4.3.2 [email protected] github.com
github.com/nodeca/js-yaml/commit/3485bc06ff8a0251505f44a00414d90df2466639 [email protected] github.com
github.com/nodeca/js-yaml/releases/tag/3.15.2 [email protected] github.com
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NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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