What’s Vulnerable › Vulnerabilities

CVE-2025-15265: Svelte 5.46.0 - Hydratable Key Script-Breakout XSS (SSR)

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-01-15 · updated 2026-06-17
• Weakness: CWE-79

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.

Affected products

• sveltejs svelte: from 5.46.0 before 5.46.3 — fixed in 5.46.3

How to fix

Upgrade to a fixed version: sveltejs svelte 5.46.3. Check the vendor advisory for mitigations.

References

• https://fluidattacks.com/advisories/lydian
• https://fluidattacks.com/advisories/lydian
• https://fluidattacks.com/advisories/lydian
• https://fluidattacks.com/advisories/lydian
• https://github.com/sveltejs/svelte/security/advisories/GHSA-6738-r8g5-qwp3

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