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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

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

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

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

O3 pinpoints whether GHSA-f3cj-j4f6-wq85 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

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

Fix: sveltejs/svelte@a16ebc6

GHSA-f3cj-j4f6-wq85 is a security vulnerability in svelte. O3 Security confirms whether GHSA-f3cj-j4f6-wq85 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

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

5.3Mdownloads / 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

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for svelte. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-f3cj-j4f6-wq85 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

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 detects GHSA-f3cj-j4f6-wq85 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works