What is CVE-2026-42567?

CVE-2026-42567 is a high-severity vulnerability in Svelte, classified under Inefficient Regular Expression Complexity. CVSS score: 7.5/10. Published 2026-06-09.

How severe is CVE-2026-42567?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Svelte

CVE-2026-42567

Svelte is a performance oriented web framework. From version 5.51.5 to before version 5.55.7, an internal regex in the Svelte runtime can take exponential time to test in <svelte:element this={tag}></svelte:element>. This issue has been pa…

Vulnerability class: ReDoS (Regular Expression Denial of Service)

EPSS: 0.004 (34.6th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Svelte
Sveltejs Svelte — versions >= 5.51.5, < 5.55.7

Weakness classification (CWE)

CWE-1333 — Inefficient Regular Expression Complexity

References

security-advisories@github.com (Product, x_refsource_MISC, Release Notes)
security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)

Frequently asked questions

What is CVE-2026-42567?: CVE-2026-42567 is a high-severity vulnerability in Svelte, classified under Inefficient Regular Expression Complexity. CVSS score: 7.5/10. Published 2026-06-09.
How severe is CVE-2026-42567?: High severity. CVSS v3 base score is 7.5 out of 10.