GHSA-f3cj-j4f6-wq85
Svelte: SSR XSS via Insecure Promise Serialization in hydratable
GHSA-f3cj-j4f6-wq85 is a medium vulnerability (CVSS 5.3) in svelte, published May 14, 2026. No source lists public exploit code. Fixed in svelte 5.55.7.
- Severity
- 5.3 MediumCVSS 4.0, GitHub Advisories
- Exploit chance
- UnscoredNo EPSS score yet
- Exploitation
- None knownNot on CISA’s or ENISA’s lists
- Fixed in
5.55.7svelte +1 more
Description
Contents 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])
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- None
Affected packages
What each source reports
GitHub Advisories Score used
Svelte: SSR XSS via Insecure Promise Serialization in hydratable
Contents 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])
- Record
GHSA-f3cj-j4f6-wq85- CVSS 4.0
- 5.3 Medium
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 - Weakness
- CWE-79
- Updated
- 2026-11-02
OSV
Svelte: SSR XSS via Insecure Promise Serialization in hydratable
Contents 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])
- Record
GHSA-f3cj-j4f6-wq85- CVSS 4.0
- 5.3 Medium
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 - Weakness
- CWE-79
- Updated
- 2026-11-02
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | GitHub Advisories, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.