CVE-2026-23957: seroval DOS Vulnerability

CVE-2026-23957 Overview

CVE-2026-23957 is a denial of service vulnerability affecting seroval, a JavaScript library that facilitates value stringification including complex structures beyond standard JSON.stringify capabilities. The vulnerability exists in versions 1.4.0 and below, where an attacker can override encoded array lengths by replacing them with excessively large values, causing the deserialization process to significantly increase processing time and consume excessive resources.

Critical Impact

Applications using vulnerable versions of seroval for deserialization may be susceptible to denial of service attacks, where maliciously crafted serialized data can cause significant processing delays and potential service unavailability.

Affected Products

• seroval versions 1.4.0 and below

Discovery Timeline

• 2026-01-22 - CVE CVE-2026-23957 published to NVD
• 2026-01-22 - Last updated in NVD database

Technical Details for CVE-2026-23957

Vulnerability Analysis

This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). The core issue lies in how seroval handles array length values during deserialization. When processing serialized data, the library trusts the encoded array length values without proper validation or bounds checking. An attacker can craft malicious serialized payloads that contain artificially inflated array length values, causing the deserializer to allocate excessive resources or enter computationally expensive processing loops.

The vulnerability can be exploited remotely over the network without requiring authentication or user interaction. While it does not compromise data confidentiality or integrity, it can severely impact the availability of applications that rely on seroval for deserializing untrusted input.

Root Cause

The root cause is the absence of proper validation and resource limits when processing array length metadata during deserialization. The library directly uses the encoded array length values to drive processing logic without sanitizing or capping these values, allowing attackers to trigger resource exhaustion through algorithmic complexity attacks.

Attack Vector

An attacker exploits this vulnerability by sending specially crafted serialized data to an application that uses seroval for deserialization. The malicious payload contains array structures with encoded lengths set to extremely large values. When the application attempts to deserialize this data, the processing time increases dramatically due to the library attempting to handle the oversized array declarations. This can result in:

• CPU exhaustion as the deserializer processes the manipulated data
• Potential memory exhaustion depending on implementation behavior
• Service degradation or complete unavailability for legitimate users

The attack requires network access to the vulnerable application endpoint that processes serialized data, but does not require any privileges or user interaction to execute.

Detection Methods for CVE-2026-23957

Indicators of Compromise

• Unusual CPU utilization spikes on servers processing seroval deserialization
• Application log entries showing extended deserialization times or timeouts
• Network traffic containing abnormally large serialized payloads to application endpoints
• Service degradation or unresponsiveness in applications using seroval

Detection Strategies

• Monitor application performance metrics for unexpected increases in request processing time
• Implement logging around deserialization operations to track processing duration anomalies
• Audit dependencies using npm audit or similar tools to identify vulnerable seroval versions
• Review inbound data sizes to identify payloads with abnormally large array declarations

Monitoring Recommendations

• Deploy application performance monitoring (APM) tools to track deserialization latency
• Set up alerts for sustained high CPU usage on systems processing serialized data
• Monitor request timeout rates and error logs for patterns indicating exploitation attempts
• Track seroval library usage across your application portfolio for vulnerability exposure

How to Mitigate CVE-2026-23957

Immediate Actions Required

• Update seroval to version 1.4.1 or later immediately
• Audit applications to identify all instances where seroval is used for deserialization
• Implement input validation and size limits on data accepted for deserialization
• Consider rate limiting on endpoints that process serialized data as a temporary measure

Patch Information

The vulnerability has been fixed in seroval version 1.4.1. The patch introduces proper validation of array length values during deserialization to prevent resource exhaustion attacks. The fix can be reviewed in the GitHub commit ce9408ebc87312fcad345a73c172212f2a798060. For detailed information about the vulnerability, refer to the GitHub Security Advisory GHSA-66fc-rw6m-c2q6.

Workarounds

• Implement request timeouts and circuit breakers around deserialization operations
• Add payload size limits at the application or network layer to reject oversized requests
• Consider sandboxing deserialization processes to limit resource consumption impact
• If upgrading is not immediately possible, avoid deserializing data from untrusted sources

# Configuration example
# Update seroval to the patched version
npm update seroval@1.4.1

# Or install the specific patched version
npm install seroval@^1.4.1

# Verify the installed version
npm list seroval