CVE-2025-15265
svelte vulnerable to Cross-site Scripting
Description
## Summary An XSS vulnerability exists in Svelte 5.46.0-2 resulting from improper escaping of `hydratable` keys. If these keys incorporate untrusted user input, arbitrary JavaScript can be injected into server-rendered HTML. ## Details When using the [`hydratable`](https://svelte.dev/docs/svelte/hydratable) function, the first argument is used as a key to uniquely identify the data, such that the value is not regenerated in the browser. This key is embedded into a `<script>` block in the server-rendered `<head>` without escaping unsafe characters. A malicious key can break out of the script context and inject arbitrary JavaScript into the HTML response. ## Impact This is a cross-site scripting vulnerability affecting applications that have the `experimental.async` flag enabled and use `hydratable` with keys incorporating untrusted user input. - **Impact**: Arbitrary JS execution in the client’s browser. - **Exploitability**: Remote, single-request if key is attacker-controlled. - **Typical Outcomes**: - Session/token theft - DOM defacement - CSRF bypass via injected JS - Account takeover depending on cookie/session strategy Affected applications should upgrade to a patched version immediately.
How to fix CVE-2025-15265
To remediate CVE-2025-15265, upgrade the affected package to a fixed version below.
- —upgrade to 5.46.4 or later
Is CVE-2025-15265 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- >= 5.46.0, < 5.46.4
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N |