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CVE-2026-73643— js-yaml: Exponential parsing time in the flow collections leads to denial of service

Quick assessment

Affected
nodeca js-yaml
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

js-yaml 是一个用于 JavaScript 的 YAML 解析器和生成器。在版本 5.0.0 至 5.2.2 之间，当应用程序对不受信任的输入调用 或 方法时，解析一个小型 YAML 文档可能会耗费指数级时间。 具体而言，在 文件中， 函数在识别到流式序列条目为键值对时，会调用 并再次调用 。如果该键本身是一个具有相同嵌套结构的流式序列，则每一层都将被重复解析两次，从而导致工作量呈 O(2ⁿ) 增长。这使得即使输入不到 200 字节，也可能使单个 CPU 核心持续繁忙数分钟，阻塞 Node.js 的事件循环，

CVSS 7.5 · High EPSS 0.49% · P40

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 1

VendorProduct Version RangeStatus
nodeca js-yaml >= 5.0.0, < 5.2.2 affected
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I. Basic Information for CVE-2026-73643

Vulnerability Information
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Vulnerability Title
js-yaml: Exponential parsing time in the flow collections leads to denial of service
Source: CVE Program / CVE List V5
Vulnerability Description
js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 until 5.2.2, parsing a small YAML document can take exponential time when an application calls load() or loadAll() on untrusted input. In src/parser/parser.ts, readFlowCollection uses restoreState and calls parseNode a second time when a flow-sequence entry is recognized as a key: value pair. If the key is a nested flow sequence of the same shape, every level is parsed twice, causing O(2^n) work and allowing an input under 200 bytes to keep one CPU busy for minutes, block the Node.js event loop, and stall the process. No anchors, aliases, merges, tags, or nondefault options are required. This issue is fixed in version 5.2.2.
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
算法复杂性
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
nodeca js-yaml >= 5.0.0, < 5.2.2 -

II. Public POCs for CVE-2026-73643

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claude_code · 6313 chars
GitHub 复现环境（可 clone 直接跑）
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III. Intelligence Information for CVE-2026-73643

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Patches & Fixes for CVE-2026-73643 (1)

Vendor Advisories for CVE-2026-73643 (1)

IV. Related Vulnerabilities

Same product: js-yaml
Same vendor: nodeca
Same weakness: CWE-407

V. Comments for CVE-2026-73643

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