CVE-2026-82260: Svelte SvelteKit DOS Vulnerability

CVE-2026-82260 Overview

CVE-2026-82260 is a memory exhaustion vulnerability in SvelteKit (@sveltejs/kit), the official application framework for Svelte. The flaw affects versions >=2.49.0 and <=2.52.1 when the experimental remote functions feature (experimental.remoteFunctions) is enabled with form support. Attackers can submit malformed form data to remote form endpoints, triggering excessive memory allocation during deserialization. The resulting resource consumption crashes the Node.js server process and produces a denial-of-service condition. The maintainers addressed the issue in version 2.52.2.

Critical Impact
Unauthenticated network attackers can crash SvelteKit application servers by sending malformed remote form payloads, causing sustained denial of service.

Affected Products

SvelteKit (@sveltejs/kit) >=2.49.0
SvelteKit (@sveltejs/kit) <=2.52.1
Node.js applications using experimental.remoteFunctions with form support enabled

Discovery Timeline

2026-08-28 - CVE-2026-82260 published to NVD
2026-08-31 - Last updated in NVD database

Technical Details for CVE-2026-82260

Vulnerability Analysis

SvelteKit's experimental remote functions feature lets client code call server functions directly, including submissions through remote forms. The framework deserializes incoming form payloads on the server before dispatching them to the handler. The affected deserialization path does not enforce bounds on the structures it reconstructs from untrusted input. An attacker crafts a malformed form body that instructs the deserializer to allocate large or deeply nested objects. The Node.js process consumes available heap memory and terminates, taking the application offline. This condition maps to CWE-400: Uncontrolled Resource Consumption.

Root Cause

The root cause is missing input validation and size limits during remote form deserialization. The parser accepts untrusted structural directives from HTTP form data without verifying that requested allocations remain within safe bounds. Because the feature is exposed over the network and requires no authentication, any client that can reach a remote form endpoint can trigger the allocation path.

Attack Vector

Exploitation requires network access to a SvelteKit application that has enabled experimental.remoteFunctions and remote form support. The attacker issues HTTP POST requests carrying malformed form payloads to a remote form route. Each request triggers oversized allocations, and repeated requests amplify pressure on the Node.js heap until the process exits. The vulnerability affects availability only; confidentiality and integrity are not impacted.

No verified public proof-of-concept is available at the time of publication. See the SvelteKit GitHub Security Advisory and the VulnCheck Advisory for SvelteKit for technical details.

Detection Methods for CVE-2026-82260

Indicators of Compromise

Repeated FATAL ERROR: JavaScript heap out of memory or Allocation failed messages in Node.js logs for the SvelteKit process.
Unexpected restarts of the SvelteKit application by process supervisors such as pm2, systemd, or container orchestrators.
High-volume POST traffic to remote form endpoints from a single source or a small set of sources.
Malformed Content-Type: application/x-www-form-urlencoded or multipart/form-data bodies targeting remote function routes.

Detection Strategies

Inventory production dependencies and flag any deployment shipping @sveltejs/kit between 2.49.0 and 2.52.1 inclusive.
Audit SvelteKit configuration for experimental.remoteFunctions with form support enabled and prioritize those workloads.
Correlate application crash events with inbound HTTP request patterns to identify request-driven memory exhaustion.

Monitoring Recommendations

Track Node.js resident set size (RSS) and heap-used metrics per SvelteKit instance and alert on sustained growth.
Monitor request rates and payload sizes to remote form paths and alert on abnormal spikes.
Ingest application, reverse-proxy, and orchestrator logs into a central analytics platform to correlate crashes with request bursts.

How to Mitigate CVE-2026-82260

Immediate Actions Required

Upgrade @sveltejs/kit to version 2.52.2 or later across all environments.
If upgrading is not immediately possible, disable experimental.remoteFunctions or turn off form support for remote functions.
Restrict access to SvelteKit remote form endpoints at the reverse proxy or WAF layer until patching completes.

Patch Information

The SvelteKit maintainers released the fix in version 2.52.2. Refer to the SvelteKit GitHub Security Advisory GHSA-vrhm-gvg7-fpcf for advisory details and the corresponding release notes.

Workarounds

Disable the experimental remote functions feature in svelte.config.js until the upgrade is applied.
Enforce request body size limits and rate limiting for remote form routes at the ingress or WAF layer.
Run SvelteKit behind a process supervisor with automatic restart and resource caps to limit blast radius during exploitation attempts.

bash

# Configuration example
# 1. Upgrade SvelteKit to the fixed release
npm install @sveltejs/kit@2.52.2

# 2. Verify the installed version
npm ls @sveltejs/kit

# 3. Temporary mitigation: disable experimental remote functions in svelte.config.js
#    export default {
#      kit: {
#        experimental: {
#          remoteFunctions: false
#        }
#      }
#    };