CVE-2026-59868

js-yaml: YAML merge-key chains can force quadratic CPU consumption

HIGH
7.5
CVSS Score
Published: July 8, 2026 at 03:18 PM UTC
Updated: October 25, 2026 at 08:10 PM UTC
1 product affected across 1 vendorJs Yaml

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Severity
HIGH7.5
Exploit prediction
EPSS 0.6%
SSVC
PoC

Description

js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 before 5.2.0, when merge keys are enabled, js-yaml can spend quadratic CPU time parsing a document whose size grows only linearly when a chain of mappings uses merge keys where each mapping merges the previous one. This issue is fixed in version 5.2.0.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

5.0.0 ≤ v < 5.2.0
Affected range stops below 5.2.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (3)

x_refsource_CONFIRMExploitVendor Advisory
Source: cverecord
https://github.com/nodeca/js-yaml/security/advisories/GHSA-g796-fgmg-93mv
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/nodeca/js-yaml/releases/tag/5.2.0

SSVC — Action Prioritization

SSVCPoCAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-407CWE-770

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