Quick answers
- Is CVE-2026-27125 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-27125 being exploited in the wild.
- How severe is CVE-2026-27125?
- Medium severity, with a CVSS score of 4, published 19 February 2026.
- Which products and versions are affected?
- svelte (npm) SEMVER:introduced=0,fixed=5.51.5.
- Is there a fix for CVE-2026-27125?
- Yes. svelte (npm): upgrade to 5.51.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-27125 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-27125?
- Check whether you run svelte (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- svelte (npm): upgrade to 5.51.5 or later
npm install svelte@5.51.5
Technical details
The vulnerability exists in Svelte's server-side rendering (SSR) implementation for attribute spreading (e.g., <div {...attrs}>). When spreading object properties, the code enumerates inherited properties from the prototype chain instead of using only own properties. This is a prototype pollution exposure: in environments where Object.prototype has been polluted by another library or code, the inherited polluted properties are included in the SSR output. The attack requires a precondition (Object.prototype pollution) and affects only SSR; client-side rendering is unaffected. The vulnerability was fixed in Svelte 5.51.5 (commit 73098bb).
Affected products
- Svelte Svelte <=5.51.4
Identifiers
- CVE-2026-27125
- GHSA-crpf-4hrx-3jrp
Timeline
- 2026-02-19: disclosed
- 2026-02-19: patched: Fixed in version 5.51.5