Svelte SSR vulnerable to cross-site scripting via spread attributes (CVE-2026-42599) | HOL Guard CVE

Medium severityCVE-2026-42599GHSA-PR6F-5X2Q-RWFP

Svelte SSR vulnerable to cross-site scripting via spread attributes

Answer in brief

CVE-2026-42599 records a Medium severity vulnerability in Svelte SSR vulnerable to cross-site scripting via spread attributes. The current sources do not mark it as known exploited. The current feed maps svelte (npm). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published May 14, 2026Updated Jun 9, 2026Source checked Sep 17, 2026First seen by HOL Jun 11, 2026Material review Jun 9, 2026

Upstream Advisory

Key facts

Risk: Medium
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps svelte (npm). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
sveltenpm	<=5.55.6	5.55.7

Recommended response

Check inventory. Check lockfiles and deployed manifests for svelte.
Review the reported fix. Update svelte to 5.55.7 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
May 14, 2026
Evidence: source:ghsa:source_dates:source-dates:record
Source modified
Jun 9, 2026
Evidence: source:ghsa:source_dates:source-dates:record
First seen by HOL
Jun 11, 2026

Sources and claim methodology

Upstream source description

When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. Note that this vulnerability _only_ triggers if the user's browser has JavaScript enabled but Svelte's hydration mechanism does not reach the vulnerable element before the event fires. This is similar to but different from [CVE-2026-27121](https://nvd.nist.gov/vuln/detail/CVE-2026-27121).

Quoted source text, attributed separately from HOL analysis.