CVE-2026-116584 in Seroval
Summary
by MITRE • 10/26/2026
Seroval facilitates JavaScript value stringification, including complex structures beyond JSON.stringify capabilities. From 1.4.1 until 1.6.8, fromJSON and fromCrossJSON do not require an array node's element list to be an actual array. A small crafted payload can supply an attacker-controlled length that determines memory allocation and decoder iterations independently of payload size, allowing an unauthenticated request to exhaust the process or block its thread. This issue is a residual bypass of the remediation for CVE-2026-23957. This issue is fixed in version 1.6.8.
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Analysis
by VulDB Data Team • 10/27/2026
The vulnerability identified in Seroval versions ranging from 1.4.1 to 1.6.8 represents a critical input validation failure within the library's deserialization mechanisms, specifically affecting the fromJSON and fromCrossJSON functions. These utilities are designed to facilitate JavaScript value stringification and parsing, offering capabilities that extend beyond standard JSON.stringify limitations by handling complex data structures. However, the implementation contains a logical flaw where it fails to strictly enforce type constraints on array node element lists during the decoding process. In a correctly implemented parser, an input designated as an array must contain elements that are themselves arrays or valid list items depending on the specific serialization format. The vulnerability arises because Seroval does not verify whether the provided structure for an array's contents is actually an array type before proceeding with parsing operations. This lack of rigorous type checking allows a malicious actor to supply crafted input where the structural integrity expected by the parser is artificially maintained through non-array data structures that mimic the necessary metadata fields, particularly those governing length and iteration counts.
This technical flaw directly enables a severe denial-of-service condition through resource exhaustion. Because the decoder relies on attacker-controlled values within these malformed structures to determine memory allocation sizes and loop iterations for decoding, an unauthenticated request can manipulate these parameters independently of the actual payload size. An adversary can craft a small but carefully constructed input that specifies excessively large length values or iteration counts. When Seroval processes this input, it allocates significant amounts of system memory based on the fraudulent length parameter and initiates processing loops corresponding to the inflated count. This discrepancy between the minimal data provided and the massive resources requested leads to rapid depletion of available heap space or CPU cycles. The result is a complete exhaustion of process resources or blocking of the primary thread, effectively rendering the service unavailable to legitimate users without requiring any form of authentication.
The operational impact of this vulnerability extends beyond simple availability loss. In environments where Seroval is used for high-throughput data processing or real-time communication channels, such as WebSocket connections or API endpoints handling serialized state updates, a successful exploitation can cause cascading failures across dependent services. The blocking of threads prevents the application from handling new requests, leading to timeouts and potential crashes in upstream load balancers or reverse proxies that monitor service health. Furthermore, because this issue is identified as a residual bypass of the remediation for CVE-2026-23957, it indicates that previous security patches addressed related but distinct aspects of input validation while overlooking this specific type confusion scenario. This highlights the complexity of securing deserialization libraries where multiple layers of structural assumptions must be validated simultaneously to prevent all forms of abuse.
From a classification perspective, this vulnerability aligns with CWE-20 Improper Input Validation and CWE-787 Out-of-bounds Write if the memory allocation leads to buffer overruns, though in this specific case, it primarily manifests as CWE-400 Uncontrolled Resource Consumption. The attack vector is consistent with ATT&CK technique T1496 Resource Hijacking, where an attacker consumes system resources to degrade performance or cause a denial of service. Additionally, the mechanism of exploiting deserialization logic falls under the broader category of insecure deserialization vulnerabilities often associated with CWE-502 Deserialization of Untrusted Data. The fact that it bypasses previous fixes underscores the need for comprehensive regression testing and deeper static analysis when patching complex parsing libraries to ensure no residual logical flaws remain exploitable by determined adversaries.
To mitigate this vulnerability, organizations must immediately upgrade Seroval to version 1.6.8 or later, where the strict type checking for array node element lists has been implemented. Until an update can be applied in environments with extended release cycles, defensive coding practices should be employed at the application layer wrapping the library calls. This includes implementing rigorous input validation that verifies not only the syntax of incoming serialized data but also its semantic structure against expected schemas before passing it to Seroval's parsing functions. Rate limiting and request size restrictions can provide additional layers of defense by capping the maximum allowable payload sizes, thereby reducing the effectiveness of resource exhaustion attacks even if malformed inputs are processed. Monitoring for unusual spikes in memory usage or thread blocking events associated with deserialization operations is also recommended as an early warning indicator of potential exploitation attempts.