Is CVE-2026-59868 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-59868 being exploited in the wild.

How severe is CVE-2026-59868?

Medium severity, with a CVSS score of 5.3, published 8 July 2026.

Which products and versions are affected?

js-yaml (npm) >= 5.0.0, <= 5.1.0, SEMVER:introduced=5.0.0,fixed=5.2.0.

Is there a fix for CVE-2026-59868?

Yes. js-yaml (npm): upgrade to 5.2.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-59868 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-59868?

Check whether you run js-yaml (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-59868: js-yaml denial of service via quadratic CPU consumption in merge keys

Q: Is there a fix for CVE-2026-59868?

Yes. js-yaml (npm): upgrade to 5.2.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-59868 attacked?

It is attacked over the network, in a software library.

Q: Am I affected by CVE-2026-59868?

Check whether you run js-yaml (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-59868 · Severity: medium · CVSS 5.3 · Published 2026-07-08

A vulnerability in the js-yaml library, which is used to parse YAML configuration files, can allow an attacker to crash or slow down an application. By providing a specially crafted YAML file with complex 'merge key' chains, an attacker can force the system to consume excessive processor power. This can lead to a denial-of-service (DoS) condition, making the affected service unavailable to legitimate users.

Technologies: js-yaml (npm). Vendors: npm.

Quick answers

Is CVE-2026-59868 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-59868 being exploited in the wild.
How severe is CVE-2026-59868?: Medium severity, with a CVSS score of 5.3, published 8 July 2026.
Which products and versions are affected?: js-yaml (npm) >= 5.0.0, <= 5.1.0, SEMVER:introduced=5.0.0,fixed=5.2.0.
Is there a fix for CVE-2026-59868?: Yes. js-yaml (npm): upgrade to 5.2.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-59868 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-59868?: Check whether you run js-yaml (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

js-yaml (npm): upgrade to 5.2.0 or later
```
npm install js-yaml@5.2.0
```

Technical details

The js-yaml library (v5.x) is susceptible to an algorithmic complexity vulnerability (CWE-407) when processing YAML merge keys (<<). When merge keys are enabled, a chain of mappings where each mapping merges the previous one causes the loader to repeatedly enumerate inherited keys. This results in O(N^2) CPU work for an O(N) input size. An attacker can exploit this by submitting a relatively small YAML document (e.g., <100KB) that requires significant processing time, leading to uncontrolled resource consumption (CWE-400). The vulnerability is mitigated in version 5.2.0 by implementing a limit on the total number of merged keys per parse call.

Affected products

nodeca js-yaml >= 5.0.0, <= 5.1.0

Identifiers

CVE-2026-59868
GHSA-g796-fgmg-93mv

Timeline

2026-07-02: disclosed: Vulnerability published to nodeca/js-yaml
2026-07-08: advisory: Published to the National Vulnerability Database (NVD)
2026-07-20: patched: GitHub Advisory reviewed and updated with patch information

References

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