CVE-2026-42567

Svelte: ReDoS in `<svelte:element>` Tag Validation

State: Published
Severity: 5.9 Medium
Published: Jun 9, 2026
Updated: Jun 9, 2026
Reserved: Apr 28, 2026

Description

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 patched in version 5.55.7.

Scores

CVSS	Score	Vector	Source
4.0	5.9 Medium	CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N	GitHub_M

Weaknesses

CWE-1333 Inefficient Regular Expression Complexity

Affected Products

Product	Versions
sveltesveltejs	>= 5.51.5, < 5.55.7Affected

References

https://github.com/sveltejs/svelte/security/advisories/GHSA-9rmh-mm8f-r9h6
https://github.com/sveltejs/svelte/releases/tag/svelte%405.55.7

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