CVE-2026-27125 MEDIUM

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

Vendor Sveltejs
Product svelte
Weakness CWE-915
Published February 20, 2026
Last update February 25, 2026

CVSS base score

5.3/10
Attack vector Network
Attack complexity High
Privileges required Low
User interaction None
Confidentiality
Integrity

CVSS 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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

February 20, 2026 CVE published
February 25, 2026 Record updated