How severe is CVE-2026-53550?

CVE-2026-53550 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-53550 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-53550?

CVE-2026-53550 affects Nodeca Js-yaml. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-53550?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-53550 have an EU (EUVD) identifier?

Yes. CVE-2026-53550 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38256.

When was CVE-2026-53550 published?

CVE-2026-53550 was published on 2026-06-22 and last updated on 2026-06-29.

CVE-2026-53550

CVE-2026-53550 is a medium-severity vulnerability in Nodeca Js-yaml with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-407.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (17th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-38256
Weakness: CWE-407
Affected product: Nodeca Js-yaml
Published: 2026-06-22
Last modified: 2026-06-29

Description

js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0 and 3.15.0, a crafted YAML document can trigger algorithmic CPU exhaustion in js-yaml merge-key processing (<<) by repeating the same alias many times in a merge sequence. This causes quadratic parse-time behavior relative to input size and can block a Node.js worker/event loop for seconds with a relatively small payload (tens of KB), resulting in denial of service. The issue is in merge handling inside lib/loader.js. This vulnerability is fixed in 4.2.0 and 3.15.0.

Frequently asked questions

What is CVE-2026-53550?: js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0 and 3.15.0, a crafted YAML document can trigger algorithmic CPU exhaustion in js-yaml merge-key processing (<<) by repeating the same alias many times in a merge sequence. This causes quadratic parse-time behavior relative to input size and can block a Node.js worker/event loop for seconds with a relatively small payload (tens of KB), resulting in denial of service. The issue is in merge handling inside lib/loader.js. This vulnerability is fixed in 4.2.0 and 3.15.0.
How severe is CVE-2026-53550?: CVE-2026-53550 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-53550 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-53550?: CVE-2026-53550 affects Nodeca Js-yaml. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-53550?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-53550 have an EU (EUVD) identifier?: Yes. CVE-2026-53550 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38256.
When was CVE-2026-53550 published?: CVE-2026-53550 was published on 2026-06-22 and last updated on 2026-06-29.

References

https://github.com/nodeca/js-yaml/security/advisories/GHSA-h67p-54hq-rp68

Affected products (1)

cpe:2.3:a:nodeca:js-yaml:*:*:*:*:*:node.js:*:*

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