How severe is GHSA-f3cj-j4f6-wq85?

No CVSS score has been assigned to GHSA-f3cj-j4f6-wq85 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-f3cj-j4f6-wq85?

GHSA-f3cj-j4f6-wq85 affects the following packages: svelte (npm). Ecosystems affected: npm.

How do I fix GHSA-f3cj-j4f6-wq85?

Update svelte to 5.55.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f3cj-j4f6-wq85 is resolved across your whole dependency graph.

How do I detect GHSA-f3cj-j4f6-wq85 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for svelte, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-f3cj-j4f6-wq85 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

How does O3 Security protect against GHSA-f3cj-j4f6-wq85?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-f3cj-j4f6-wq85 can be triaged on real exposure rather than presence alone.

Is GHSA-f3cj-j4f6-wq85 actively exploited in the wild?

No public exploit code has been indexed for GHSA-f3cj-j4f6-wq85 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-f3cj-j4f6-wq85 published, and has it been updated?

GHSA-f3cj-j4f6-wq85 was published on May 14, 2026 and was last updated on May 14, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

GHSA-f3cj-j4f6-wq85 — svelte

Fix: sveltejs/svelte@a16ebc6

GHSA-f3cj-j4f6-wq85 is a security vulnerability in svelte. A fix is available for svelte — see the affected versions and patch details below.

Svelte: SSR XSS via Insecure Promise Serialization in hydratable

Published

May 14, 2026

Updated

May 14, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of May 14, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

2Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

sveltenpm

6.8Mdownloads / week

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])

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`svelte`	≥ 5.46.0&&< 5.55.7	5.55.7`npm install svelte@5.55.7`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for svelte, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update svelte to 5.55.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f3cj-j4f6-wq85 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-f3cj-j4f6-wq85 can be triaged on real exposure rather than presence alone.

Tailored to GHSA-f3cj-j4f6-wq85. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

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])`

O3 Security · Impact-Aware SCA

Is GHSA-f3cj-j4f6-wq85 in your dependencies?

O3 Security finds GHSA-f3cj-j4f6-wq85 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works