CVE-2026-27125
Prototype Pollution Exposure via Attribute Spreading in Svelte SSR
Publication date: 2026-02-20
Last updated on: 2026-02-23
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| svelte | svelte | to 5.51.5 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-915 | The product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in the Svelte web framework prior to version 5.51.5 during server-side rendering (SSR). When using attribute spreading on elements (e.g., <div {...attrs}>), the framework incorrectly enumerates inherited properties from the object's prototype chain instead of only its own properties.
If the Object.prototype has been polluted (i.e., modified with additional properties), which is outside of Svelte's control, this can cause unexpected attributes to appear in the SSR output or cause SSR to throw errors.
This issue does not affect client-side rendering and was fixed in Svelte version 5.51.5.
How can this vulnerability impact me? :
The vulnerability can lead to unexpected attributes appearing in the server-side rendered HTML output or cause server-side rendering to throw errors.
This may result in incorrect or malformed HTML being sent to clients, potentially affecting the functionality or appearance of web pages.
Additionally, SSR errors could cause server instability or downtime, impacting the availability of the web application.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, upgrade the Svelte framework to version 5.51.5 or later, where the issue has been fixed.