Vulnerability in Svelte
CVE-2026-27125
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.
Vulnerability class: Mass Assignment
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.005 (40.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 40th percentile — 40.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.001
Affected products
- Svelte
- Sveltejs Svelte — versions < 5.51.5
Weakness classification (CWE)
References
- github.com/sveltejs/svelte/security/advisories/GHSA-crpf-4hrx-3jrp (Vendor Advisory)
- github.com/sveltejs/svelte/commit/73098bb26c6f06e7fd1b0746d817d2c5ee90755f (Patch)
- github.com/sveltejs/svelte/releases/tag/svelte@5.51.5 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-27125?
- CVE-2026-27125 is a medium-severity vulnerability in Svelte, classified under Improperly Controlled Modification of Dynamically-Determined Object Attributes. CVSS score: 6.8/10. Published 2026-02-20.
- How severe is CVE-2026-27125?
- Medium severity. CVSS v3 base score is 6.8 out of 10.