CVE-2026-23737 in seroval
Summary
by MITRE • 01/22/2026
seroval facilitates JS value stringification, including complex structures beyond JSON.stringify capabilities. In versions 1.4.0 and below, improper input handling in the JSON deserialization component can lead to arbitrary JavaScript code execution. Exploitation is possible via overriding constant value and error deserialization, allowing indirect access to unsafe JS evaluation. At minimum, attackers need the ability to perform 4 separate requests on the same function, and partial knowledge of how the serialized data is used during later runtime processing. This vulnerability affects the fromJSON and fromCrossJSON functions in a client-to-server transmission scenario. This issue has been fixed in version 1.4.0.
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Analysis
by VulDB Data Team • 01/23/2026
The vulnerability identified as CVE-2026-23737 resides within the seroval library, a tool designed to facilitate JavaScript value stringification beyond the limitations of standard JSON.stringify capabilities. This library operates by handling complex data structures that traditional JSON serialization cannot process, making it a critical component in applications requiring robust data transformation between client and server environments. The flaw specifically manifests in versions 1.4.0 and earlier, where the JSON deserialization component demonstrates inadequate input validation and handling mechanisms that create exploitable conditions for arbitrary code execution.
The technical implementation of this vulnerability stems from improper input handling within the JSON deserialization process, creating a path for attackers to manipulate serialized data structures. When the library processes data through its fromJSON and fromCrossJSON functions during client-to-server transmission scenarios, it fails to properly validate or sanitize input parameters. This weakness allows malicious actors to construct specially crafted serialized data that, when processed, triggers unsafe JavaScript evaluation patterns. The vulnerability operates through indirect means rather than direct code injection, requiring attackers to leverage constant value overriding and error deserialization techniques to achieve their objectives.
The operational impact of this vulnerability extends beyond simple code execution, as it represents a sophisticated attack vector that requires specific conditions to be met. Attackers must execute four separate requests against the same function to establish the necessary conditions for exploitation, indicating a multi-step attack methodology that complicates detection and mitigation. The attack requires partial knowledge of how serialized data is processed during runtime, suggesting that the vulnerability is particularly dangerous in environments where the internal processing logic of the application is not fully understood or properly isolated. This characteristic places the vulnerability in the category of advanced persistent threats that can be difficult to detect through conventional security measures.
The exploitation of this vulnerability directly relates to CWE-74 and CWE-94 categories, which address injection flaws and code execution vulnerabilities respectively. The attack pattern aligns with ATT&CK techniques involving command and control through serialized objects, specifically targeting the execution of arbitrary code through deserialization vulnerabilities. The fact that this issue was resolved in version 1.4.0 indicates that the developers implemented proper input validation and sanitization mechanisms to prevent the manipulation of constant values during deserialization processes. Organizations using affected versions should prioritize immediate patching to prevent potential exploitation, as the vulnerability could enable attackers to execute malicious code on targeted systems with the same privileges as the affected application. The mitigation strategy should include comprehensive input validation, proper error handling, and regular security assessments to identify similar vulnerabilities in other components of the application stack.