# CVE-2026-84375 — nodeca js-yaml

> As of 2026-09-02, CVE-2026-84375 is a HIGH-severity vulnerability in nodeca js-yaml, CVSS v3.1 7.5, EPSS 0.3% (31.5th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-84375 as of 2026-09-02; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-09-02

## What is CVE-2026-84375?

js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 until 3.15.2 and 4.3.2, maxTotalMergeKeys in lib/js-yaml/loader.js and lib/loader.js does not count empty mapping sources while processing the merge key <<. An attacker can alias a large sequence of empty mappings into many merge targets, causing O(N * K) processing while totalMergeKeys remains unchanged and the configured resource limit is never reached. A relatively small YAML document can therefore cause prolonged CPU consumption in applications that parse untrusted YAML, and merge processing is enabled by default on these release lines. This issue is fixed in versions 3.15.2 and 4.3.2.

The record classifies CVE-2026-84375 under weakness classes [CWE-400](https://intel.threadlinqs.com/cwe/CWE-400), [CWE-407](https://cwe.mitre.org/data/definitions/407.html). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 34 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.5 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 31.5% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 5/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-09-01, last modified 2026-09-02

## Is CVE-2026-84375 being exploited?

It currently carries a trending score of 37 in the Threadlinqs vulnerability feed.

## Affected products and versions

- **nodeca**: js-yaml

## How to fix CVE-2026-84375

No vendor patch reference has been recorded for CVE-2026-84375 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-84375

No threat campaign in the Threadlinqs corpus currently references CVE-2026-84375, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, FIRST EPSS. Last verified by Threadlinqs on 2026-09-03.

**Vendor advisory and patch**

- [github.com](https://github.com/nodeca/js-yaml/security/advisories/GHSA-2883-xcg3-v3hh)

**Other references**

- [github.com](https://github.com/nodeca/js-yaml/pull/797)
- [github.com (3485bc06ff8a0251505f44a00414d90df2466639)](https://github.com/nodeca/js-yaml/commit/3485bc06ff8a0251505f44a00414d90df2466639)
- [github.com (6a8e05f9a485188ed730ac81e81ae221352ef480)](https://github.com/nodeca/js-yaml/commit/6a8e05f9a485188ed730ac81e81ae221352ef480)
- [github.com (d90b6612a5a84385bdcb556c44578eac76dc0f6b)](https://github.com/nodeca/js-yaml/commit/d90b6612a5a84385bdcb556c44578eac76dc0f6b)
- [github.com (3.15)](https://github.com/nodeca/js-yaml/releases/tag/3.15.2)

_Showing 6 of 7 recorded references._

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-84375
Full detection coverage and IOCs for threats exploiting CVE-2026-84375 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp