CVE-2026-22774: Svelte Devalue DOS Vulnerability

CVE-2026-22774 Overview

CVE-2026-22774 is a Denial of Service vulnerability affecting Svelte devalue, a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. From versions 5.3.0 to 5.6.1, certain malicious inputs can cause devalue.parse to consume excessive CPU time and/or memory, potentially leading to denial of service in systems that parse input from untrusted sources.

Critical Impact

Applications using devalue.parse on externally-supplied data are vulnerable to resource exhaustion attacks that can render services unavailable.

Affected Products

• Svelte devalue versions 5.3.0 through 5.6.1

Discovery Timeline

• 2026-01-15 - CVE CVE-2026-22774 published to NVD
• 2026-01-20 - Last updated in NVD database

Technical Details for CVE-2026-22774

Vulnerability Analysis

This vulnerability is classified under CWE-405 (Asymmetric Resource Consumption). The flaw exists in the typed array hydration mechanism within the devalue.parse function. When processing serialized data, the library expects an ArrayBuffer as input for typed array reconstruction but fails to validate this assumption before creating the typed array. An attacker can exploit this by providing specially crafted input that triggers excessive memory allocation or CPU-intensive operations during the parsing process.

The vulnerability is network-accessible, requires no user interaction, and can be exploited without authentication. This makes it particularly dangerous for server-side applications that process untrusted client input through the devalue library.

Root Cause

The root cause is a missing input validation check in the typed array hydration code path. The hydrate function processes the input value without verifying that the result is actually an ArrayBuffer before passing it to the typed array constructor. When non-ArrayBuffer data is provided, the typed array constructor may exhibit undefined behavior, including resource exhaustion through excessive memory allocation or CPU consumption.

Attack Vector

An attacker can exploit this vulnerability by sending maliciously crafted serialized data to an endpoint that uses devalue.parse. The attack requires network access to the vulnerable application and can be executed remotely without any privileges or user interaction. The exploitation could cause:

1. CPU exhaustion through computationally expensive operations
2. Memory exhaustion through excessive allocations
3. Complete service unavailability (Denial of Service)

The following patch demonstrates the fix applied in version 5.6.2:

 				case 'BigInt64Array':
 				case 'BigUint64Array': {
 					const TypedArrayConstructor = globalThis[type];
-					const typedArray = new TypedArrayConstructor(hydrate(value[1]));
+					const buffer = hydrate(value[1]);
+					if (!(buffer instanceof ArrayBuffer)) {
+						throw new Error(`Invalid input, expected ArrayBuffer but got ${typeof buffer}`);
+					}
+					const typedArray = new TypedArrayConstructor(buffer);

 					hydrated[index] =
 						value[2] !== undefined

Source: GitHub Commit e46afa6

Detection Methods for CVE-2026-22774

Indicators of Compromise

• Abnormal memory consumption spikes in Node.js processes utilizing the devalue library
• Elevated CPU usage during parsing operations without corresponding legitimate workload
• Application crashes or timeouts when processing incoming serialized data
• Error logs showing memory allocation failures or out-of-memory conditions

Detection Strategies

• Monitor application resource consumption for anomalies in memory and CPU usage patterns
• Implement rate limiting on endpoints that process serialized input through devalue
• Set up alerting for Node.js process crashes or restarts related to resource exhaustion
• Audit package dependencies to identify vulnerable devalue versions (5.3.0 - 5.6.1)

Monitoring Recommendations

• Deploy application performance monitoring (APM) to track resource usage on endpoints consuming devalue parsing
• Configure process-level monitoring for Node.js applications with thresholds for memory and CPU
• Implement request timeouts to prevent long-running parse operations from blocking resources
• Enable verbose logging around devalue parsing operations for forensic analysis

How to Mitigate CVE-2026-22774

Immediate Actions Required

• Upgrade Svelte devalue to version 5.6.2 or later immediately
• Identify all applications and services using devalue for parsing untrusted input
• Implement input validation before passing data to devalue.parse
• Consider deploying resource limits (memory and CPU) for affected applications

Patch Information

The vulnerability is fixed in Svelte devalue version 5.6.2. The patch adds proper type checking to ensure the hydrated value is an ArrayBuffer before passing it to typed array constructors. Organizations should update their dependencies immediately:

• Fixed Version:5.6.2
• Security Advisory:GHSA-vw5p-8cq8-m7mv
• Release Notes:GitHub Release v5.6.2
• Patch Commit:e46afa64dd2b25aa35fb905ba5d20cea63aabbf7

Workarounds

• Validate and sanitize all input before passing to devalue.parse in untrusted contexts
• Implement resource limits using Node.js --max-old-space-size flag to constrain memory usage
• Use process managers with automatic restart capabilities to recover from resource exhaustion
• Consider wrapping devalue parsing in try-catch blocks with timeouts

# Configuration example - Set Node.js memory limits and implement process management
# Limit Node.js heap size to 512MB
node --max-old-space-size=512 your-application.js

# Using PM2 for process management with memory limits
pm2 start your-application.js --max-memory-restart 512M