GHSA-j2f3-wq62-6q46
@sveltejs/kit has memory amplification DoS vulnerability in Remote Functions binary form deserializer (application/x-sveltekit-formdata)
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
@sveltejs/kitnpmDescription
Summary
The experimental form remote function uses a binary data format containing a representation of submitted form data. A specially-crafted payload can cause the server to allocate a large amount of memory, causing DoS via memory exhaustion.
Details
When a form is submitted to a remote function endpoint, the SvelteKit client encodes the data using a custom format, and POSTs it to the endpoint as a request with an application/x-sveltekit-formdata content type.
The first few bytes of the request body encode the length of the data. SvelteKit will attempt to read the request body up until the specified offset, but if the body is not yet available then an array buffer of that size will be created eagerly to accommodate it as it arrives.
An attacker can force this code path by sending a small payload that specifies a large data length, then stalling the connection. The resulting array buffer will be held in memory, potentially causing memory exhaustion.
Impact
- Vulnerability type: Availability / memory exhaustion (memory amplification).
- Who is impacted: SvelteKit apps with
experimental.remoteFunctionsenabled, and that expose a reachable Remote Form endpoint. - Attack: an unauthenticated attacker can repeatedly open connections, send only the 8-byte header/prefix (with large data_length), and stall the body to hold large allocations, exhausting memory.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @sveltejs/kit | ≥ 2.49.0&&< 2.49.5 | 2.49.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @sveltejs/kit. 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 @sveltejs/kit to 2.49.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-j2f3-wq62-6q46 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-j2f3-wq62-6q46 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-j2f3-wq62-6q46. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-j2f3-wq62-6q46 in your dependencies?
O3 detects GHSA-j2f3-wq62-6q46 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.