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CVE-2026-84375— js-yaml: maxTotalMergeKeys does not limit CPU use for empty merge sources

Quick assessment

Affected
nodeca js-yaml
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

js-yaml 是一款用于 JavaScript 的 YAML 解析器和生成器。在 3.0.0 到 3.15.2 以及 4.3.2 之前的版本中， 和 中的 在处理合并键 时，没有统计空映射（empty mapping）来源。攻击者可以将一个包含大量空映射的大型序列通过别名（alias）映射到许多合并目标上，导致处理过程呈现 O(N * K) 的复杂度；在此期间 的计数保持不变，因此配置的资源共享限制（resource limit）永远无法达到。因此，一个相对较小的 YAML 文档就可以导致解析不可信 YAML 的

CVSS 7.5 · High
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I. Basic Information for CVE-2026-84375

Vulnerability Information
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Vulnerability Title
js-yaml: maxTotalMergeKeys does not limit CPU use for empty merge sources
Source: CVE Program / CVE List V5
Vulnerability Description
js-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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
nodeca js-yaml >= 3.0.0, < 3.15.2 -

II. Public POCs for CVE-2026-84375

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III. Intelligence Information for CVE-2026-84375

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Other References for CVE-2026-84375 (7)

IV. Related Vulnerabilities

Same product: js-yaml
Same vendor: nodeca
Same weakness: CWE-400

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