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PatchSiren cyber security CVE debrief

CVE-2026-59870 nodeca CVE debrief

CVE-2026-59870 is a vulnerability in js-yaml, a JavaScript YAML parser and dumper. The vulnerability affects versions 5.0.0 to 5.2.0 and causes O(n^2) CPU consumption when parsing crafted ordered-map documents. This issue is fixed in version 5.2.1. The vulnerability has a CVSS score of 5.3 and a severity of MEDIUM. Developers and administrators should be aware of this vulnerability and take steps to mitigate it.

Vendor
nodeca
Product
js-yaml
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-08
Original CVE updated
2026-10-06
Advisory published
2026-07-08
Advisory updated
2026-10-06

Who should care

Developers and administrators using js-yaml in their applications should be aware of this vulnerability and take steps to mitigate it. This includes updating js-yaml to version 5.2.1 or later, reviewing and validating input YAML data, and monitoring CPU consumption and performance of applications using js-yaml.

Technical summary

The vulnerability is caused by the use of omapTag.addItem() to perform a linear duplicate-key scan on every insertion in the !!omap tag in src/tag/sequence/omap.ts. This results in O(n^2) CPU consumption when yaml.load() parses a crafted ordered-map document. The vulnerability has been fixed in version 5.2.1. Affected products using js-yaml versions 5.0.0 to 5.2.0 should be updated to version 5.2.1 or later to mitigate this vulnerability. Developers and administrators should review and validate input YAML data to prevent crafted ordered-map documents and monitor CPU consumption and performance of applications using js-yaml.

Defensive priority

Medium

Recommended defensive actions

  • Update js-yaml to version 5.2.1 or later
  • Review and validate input YAML data to prevent crafted ordered-map documents
  • Monitor CPU consumption and performance of applications using js-yaml
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-07-08T16:16:33.580Z and last modified on 2026-07-10T18:01:31.563Z. The NVD entry is currently Awaiting Analysis. This information is based on the provided source corpus. Further verification is recommended to confirm affected scope and severity.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-59870 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-59870

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-59870 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-59870

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.