medium5.3
CVE-2026-27125
Svelte SSR attribute spreading includes inherited properties from prototype chain
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | svelte | <= 5.51.4 | 5.51.5 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Svelte | Svelte | before 5.51.5 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/sveltejs/svelte/commit/73098bb26c6f06e7fd1b0746d817d2c5ee90755f
- https://github.com/sveltejs/svelte/releases/tag/svelte@5.51.5
- https://github.com/sveltejs/svelte/security/advisories/GHSA-crpf-4hrx-3jrp
- https://github.com/advisories/GHSA-crpf-4hrx-3jrp
- https://nvd.nist.gov/vuln/detail/CVE-2026-27125