XSS in Svelte
CVE-2025-15265
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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (26.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 26.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.000
Affected products
- Svelte — versions 5.46.0
Weakness classification (CWE)
References
- fluidattacks.com/advisories/lydian (Exploit, Third Party Advisory, third-party-advisory)
- github.com/sveltejs/svelte/security/advisories/GHSA-6738-r8g5-qwp3 (vendor-advisory, Third Party Advisory)
Frequently asked questions
- What is CVE-2025-15265?
- CVE-2025-15265 is a medium-severity vulnerability in Svelte, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-01-15.
- How severe is CVE-2025-15265?
- Medium severity. CVSS v3 base score is 6.1 out of 10.