Svelte: SSR XSS via Insecure Promise Serialization in hydratable
Priority LOW 38CWE-79Published · Updated
Key facts
- Attack vector
- —
- Privileges required
- —
- User interaction
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- Attack complexity
- —
- Impact type
- Cross-site scripting
- Confidentiality · integrity · availability
- —
- Fix status
- Fixed
No CVSS vector from any source. Fix status from GitHub. Impact type from CWE-79.
Summary
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])`
Why it matters now
Fix Fixed svelte (npm): 5.55.7
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | svelte (npm) | 5.46.0 to before 5.55.7 | 5.55.7 | Patch available | GHSA-f3cj-j4f6-wq85 |
- svelte (npm) Vendor— Affected 5.46.0 to before 5.55.7 Fixed in 5.55.7 Patch available GHSA-f3cj-j4f6-wq85
Remediation
- Fix · GHSA-f3cj-j4f6-wq85 svelte (npm) Fixed in 5.55.7 Advisory →
Timeline
- 2026-10-03 Threatist record created from GHSA-f3cj-j4f6-wq85
References
Sources
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