CVE-2025-15265

Medium

Description

An SSR XSS exists in async hydration when attacker‑controlled keys are passed to hydratable. The key is embedded inside a <script> block without HTML‑safe escaping, allowing </script> to terminate the script and inject arbitrary JavaScript. This enables remote script execution in users' browsers, with potential for session theft and account compromise. This issue affects Svelte: from 5.46.0 before 5.46.3.

SeverityMedium

CVSS6.1

Exploit probability—

Product

Svelte

PublishedJan 15, 2026

First seenJan 15, 2026

Weakness typeCWE-79Cross-site scripting (XSS)

How to fix

Update

svelte svelte5.46.3 or later
svelte5.46.4 or later

Patches

fluidattacks.com/advisories/lydian

Vendor advisories

github.com/sveltejs/svelte/security/advisories/GHSA-6738-r8g5-qwp3

Affected products

Product	Affected versions	Fixed in
svelte svelte	5.46.0 ≤ v < 5.46.3	5.46.3
sveltenpm	5.46.0 ≤ v < 5.46.4	5.46.4

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