CVE-2026-59870
js-yaml quadratic-complexity denial of service via YAML11_SCHEMA !!omap parsing
Description
js-yaml is a JavaScript YAML parser and dumper. Prior to 3.15.1, 4.3.1, and 5.2.1, YAML11_SCHEMA support for the !!omap tag in src/tag/sequence/omap.ts uses omapTag.addItem() to perform a linear duplicate-key scan on every insertion, causing O(n^2) CPU consumption when yaml.load() parses a crafted ordered-map document. In v3 and v4, !!omap is active and exploitable by default. v5 doesn't use !!omap by default, and the chances of activating it are very low.This issue is fixed in 3.15.1, 4.3.1, and 5.2.1.
INFO
Published Date :
July 8, 2026, 4:16 p.m.
Last Modified :
Oct. 6, 2026, 4:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update js-yaml to version 5.2.1.
- Ensure all dependencies use the updated version.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-59870.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-59870 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-59870
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-59870 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-59870 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by [email protected]
Oct. 06, 2026
Action Type Old Value New Value Changed Description js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 before 5.2.1, YAML11_SCHEMA support for the !!omap tag in src/tag/sequence/omap.ts uses omapTag.addItem() to perform a linear duplicate-key scan on every insertion, causing O(n^2) CPU consumption when yaml.load() parses a crafted ordered-map document. This issue is fixed in version 5.2.1. js-yaml is a JavaScript YAML parser and dumper. Prior to 3.15.1, 4.3.1, and 5.2.1, YAML11_SCHEMA support for the !!omap tag in src/tag/sequence/omap.ts uses omapTag.addItem() to perform a linear duplicate-key scan on every insertion, causing O(n^2) CPU consumption when yaml.load() parses a crafted ordered-map document. In v3 and v4, !!omap is active and exploitable by default. v5 doesn't use !!omap by default, and the chances of activating it are very low.This issue is fixed in 3.15.1, 4.3.1, and 5.2.1. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Removed CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Added Affected Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/59xxx/CVE-2026-59870.json">CVE-2026-59870</a> Added Reference https://github.com/nodeca/js-yaml/commit/22a8071ef032117bc6249c330b240ac3aa2d3ded Added Reference https://github.com/nodeca/js-yaml/commit/39f3211a2f01b3c6982710cf21434ab7060acefe Added Reference https://github.com/nodeca/js-yaml/commit/c3cc4b0bb9ddb9af2dd9b61e0d56f5ce7983cd4a Added Reference https://github.com/nodeca/js-yaml/releases/tag/3.15.1 Added Reference https://github.com/nodeca/js-yaml/releases/tag/4.3.1 Added Reference https://github.com/nodeca/js-yaml/releases/tag/5.2.1 Added Reference https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm Removed Reference https://github.com/nodeca/js-yaml/commit/39f3211a2f01b3c6982710cf21434ab7060acefe Removed Reference https://github.com/nodeca/js-yaml/releases/tag/5.2.1 Removed Reference https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm Removed Reference Type https://github.com/nodeca/js-yaml/commit/39f3211a2f01b3c6982710cf21434ab7060acefe Types: Patch Removed Reference Type https://github.com/nodeca/js-yaml/releases/tag/5.2.1 Types: Release Notes Removed Reference Type https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm Types: Exploit, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Oct. 06, 2026
Action Type Old Value New Value Added Reference https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm Removed Reference https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm Removed Reference Type https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm Types: Exploit, Vendor Advisory -
Initial Analysis by [email protected]
Jul. 10, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-770 Added CPE Configuration OR *cpe:2.3:a:nodeca:js-yaml:*:*:*:*:*:node.js:*:* versions from (including) 5.0.0 up to (excluding) 5.2.1 Added Reference Type GitHub, Inc.: https://github.com/nodeca/js-yaml/commit/39f3211a2f01b3c6982710cf21434ab7060acefe Types: Patch Added Reference Type GitHub, Inc.: https://github.com/nodeca/js-yaml/releases/tag/5.2.1 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm Types: Exploit, Vendor Advisory Added Reference Type CISA-ADP: https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm Types: Exploit, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 08, 2026
Action Type Old Value New Value Added Reference https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm Added SSVC {'id': 'CVE-2026-59870', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-08T15:50:31.265965Z'} -
New CVE Received by [email protected]
Jul. 08, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'nodeca', 'product': 'js-yaml', 'versions': [{'status': 'affected', 'version': '>= 5.0.0, < 5.2.1'}]}] Added Description js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 before 5.2.1, YAML11_SCHEMA support for the !!omap tag in src/tag/sequence/omap.ts uses omapTag.addItem() to perform a linear duplicate-key scan on every insertion, causing O(n^2) CPU consumption when yaml.load() parses a crafted ordered-map document. This issue is fixed in version 5.2.1. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Added CWE CWE-407 Added Reference https://github.com/nodeca/js-yaml/commit/39f3211a2f01b3c6982710cf21434ab7060acefe Added Reference https://github.com/nodeca/js-yaml/releases/tag/5.2.1 Added Reference https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm