CVE-2026-73643 PUBLISHED

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

Assigner: GitHub_M
Reserved: 13.08.2026 Published: 13.08.2026 Updated: 13.08.2026

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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS Score: 7.5

Product Status

Vendor nodeca
Product js-yaml
Versions
  • Version >= 5.0.0, < 5.2.2 is affected

References

Problem Types

  • CWE-407: Inefficient Algorithmic Complexity CWE