CVE-2026-23956 in seroval
Summary
by MITRE • 01/22/2026
seroval facilitates JS value stringification, including complex structures beyond JSON.stringify capabilities. In versions 0.2.0 through 1.4.0, overriding RegExp serialization with extremely large patterns can exhaust JavaScript runtime memory during deserialization. Additionally, overriding RegExp serialization with patterns that trigger catastrophic backtracking can lead to ReDoS (Regular Expression Denial of Service). This issue has been fixed in version 1.4.1.
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Analysis
by VulDB Data Team • 05/20/2026
The vulnerability identified as CVE-2026-23956 affects the seroval library, a utility designed to facilitate JavaScript value stringification with capabilities extending beyond standard JSON.stringify functionality. This library serves as a bridge for serializing complex JavaScript data structures, including objects, arrays, and various data types that traditional JSON serialization cannot handle. The flaw resides in how the library processes regular expression objects during the serialization and deserialization processes, creating potential security risks that can impact applications relying on this dependency. The vulnerability specifically targets versions 1.4.0 and earlier, with the issue being resolved in version 1.4.1 through code modifications that address the problematic serialization handling.
The technical implementation of this vulnerability stems from improper handling of RegExp object serialization within the seroval library. When developers override RegExp serialization patterns, particularly with extremely large regular expressions, the JavaScript runtime can experience memory exhaustion during the deserialization phase. This occurs because the library does not adequately validate or limit the size of regular expression patterns being processed, allowing malicious inputs to consume excessive memory resources. Additionally, the library's handling of regular expression patterns creates opportunities for catastrophic backtracking scenarios, where carefully crafted regular expressions can cause the JavaScript engine to spend excessive computational time in pattern matching operations. This second aspect of the vulnerability manifests as Regular Expression Denial of Service, where an attacker can craft inputs that cause the application to become unresponsive or crash. The vulnerability aligns with CWE-1321 which specifically addresses issues related to regular expression denial of service and CWE-400 which covers excessive resource consumption.
The operational impact of CVE-2026-23956 extends beyond simple performance degradation to potentially compromise entire application availability and stability. When memory exhaustion occurs during deserialization, applications may crash or become unresponsive, leading to service disruption for legitimate users. The ReDoS component creates a more subtle but equally dangerous threat vector, as attackers can craft malicious inputs that cause applications to consume excessive CPU resources, potentially leading to denial of service conditions that can affect system availability. Applications using the affected seroval versions may be vulnerable to both types of attacks simultaneously, making the impact more severe than individual vulnerabilities would suggest. This vulnerability particularly affects web applications, server-side JavaScript environments, and any system that relies on complex data serialization and deserialization processes, as these scenarios are common in modern web development architectures.
Mitigation strategies for CVE-2026-23956 should prioritize immediate version upgrading to 1.4.1 or later, which contains the necessary code fixes addressing both memory exhaustion and catastrophic backtracking issues. Organizations should conduct thorough dependency audits to identify all applications and systems using affected versions of seroval and implement comprehensive testing procedures to validate that the upgrade resolves the vulnerabilities without introducing compatibility issues. Additional protective measures include implementing input validation and sanitization for any user-provided regular expression patterns, establishing resource limits and timeouts for serialization processes, and monitoring application behavior for unusual memory consumption or processing patterns. From a defensive perspective, this vulnerability highlights the importance of validating and limiting the complexity of regular expression patterns in applications, particularly those that process user input, and demonstrates how seemingly benign serialization utilities can introduce critical security risks. The ATT&CK framework categorizes this vulnerability under T1496 for resource exhaustion and T1211 for command and control, as the exploitation can lead to both availability and potentially remote code execution scenarios in vulnerable environments.