MediumGHSA-9rmh-mm8f-r9h6CVE-2026-42567

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

Published 14 May 2026 · Updated 9 Jun 2026

Affected package

Affected: >=5.51.5 <5.55.7
Fixed in: 5.55.7

Update to the fixed version for your release line, for example:npm install svelte@5.55.7

Details

An internal regex in the Svelte runtime can take exponential time to test in <svelte:element this={tag}></svelte:element>. You are only vulnerable to this if you allow tags of unconstrained length. If your application only allows a predetermined list of tags or trims their length before passing them to svelte:element, you are safe.

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References

Advisory data from OSV.dev (opens OSV.dev in a new tab), refreshed daily.