GHSA-F3CJ-J4F6-WQ85
Vulnerability from github – Published: 2026-05-14 20:30 – Updated: 2026-05-14 20:30Contents of hydratable promises were not properly stringified, potentially leading to an XSS exploit. You are vulnerable if all of the following is true:
- you are using hydratable (an experimental feature at the time of this report)
- you are passing attacker-controlled input such that a synchronous value is hydrated, then a promise value, e.g. hydratable('someKey', () => [synchronousValue, promiseValue])
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 5.55.6"
},
"package": {
"ecosystem": "npm",
"name": "svelte"
},
"ranges": [
{
"events": [
{
"introduced": "5.46.0"
},
{
"fixed": "5.55.7"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": true,
"github_reviewed_at": "2026-05-14T20:30:09Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"details": "Contents of `hydratable` promises were not properly stringified, potentially leading to an XSS exploit. You are vulnerable if all of the following is true:\n- you are using `hydratable` (an experimental feature at the time of this report)\n- you are passing attacker-controlled input such that a synchronous value is hydrated, then a promise value, e.g. `hydratable(\u0027someKey\u0027, () =\u003e [synchronousValue, promiseValue])`",
"id": "GHSA-f3cj-j4f6-wq85",
"modified": "2026-05-14T20:30:09Z",
"published": "2026-05-14T20:30:09Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/sveltejs/svelte/security/advisories/GHSA-f3cj-j4f6-wq85"
},
{
"type": "WEB",
"url": "https://github.com/sveltejs/svelte/commit/a16ebc67bbcf8f708360195687e1b2719463e1a4"
},
{
"type": "PACKAGE",
"url": "https://github.com/sveltejs/svelte"
},
{
"type": "WEB",
"url": "http://github.com/sveltejs/svelte/releases/tag/svelte%405.55.7"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Svelte: SSR XSS via Insecure Promise Serialization in hydratable"
}
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