CVE-2026-107298 in msgpack5
Summary
by MITRE • 10/08/2026
msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the array and map decoding paths have no nesting-depth limit, allowing an attacker who can provide MessagePack input to submit deeply nested containers that exhaust the JavaScript call stack and interrupt a process, worker, or request handler. This issue is fixed in version 6.1.0.
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Analysis
by VulDB Data Team • 10/08/2026
The msgpack5 library serves as a robust implementation of the MessagePack v5 serialization protocol for both Node.js environments and web browsers, facilitating efficient data interchange between systems. A critical security flaw was identified within this library prior to version 6.1.0, specifically affecting the decoding logic responsible for processing array and map structures. This vulnerability stems from an absence of a nesting-depth limit during the parsing process. When the decoder encounters nested containers such as arrays containing other arrays or maps embedded within maps, it recursively processes each level without enforcing any maximum depth constraint.
This lack of recursion control allows an attacker who can supply arbitrary MessagePack input to craft deeply nested data structures that exceed the available JavaScript call stack size. As the parser attempts to unwind these excessively deep recursive calls, it triggers a stack overflow condition. In Node.js environments, this typically results in the abrupt termination of the process or worker thread, effectively causing a denial of service for any application relying on msgpack5 for deserializing untrusted data. Similarly, in browser-based contexts, such an event can freeze the main execution thread, rendering the web page unresponsive and degrading user experience significantly.
From a classification perspective, this vulnerability aligns with CWE-787: Out-of-bounds Write or CWE-20: Improper Input Validation, specifically regarding insufficient depth checking for nested structures. It also maps to MITRE ATT&CK technique T1496: Resource Hijacking, where the attacker consumes system resources such as CPU and memory through excessive computation caused by unbounded recursion. The operational impact is primarily a denial of service rather than remote code execution or data exfiltration, although in some specific runtime configurations, stack overflows can potentially lead to undefined behavior that might be exploited further if other vulnerabilities are present.
To mitigate this risk, organizations utilizing msgpack5 must ensure they upgrade to version 6.1.0 or later, where the developers have implemented a hard limit on nesting depth during decoding operations. For applications unable to immediately update their dependencies, implementing input validation at the application layer is recommended as an interim measure. This includes validating the structure of incoming MessagePack data before passing it to the decoder and rejecting payloads that appear excessively large or complex. Additionally, deploying runtime protection mechanisms such as heap size limits or process restart policies can help contain the impact of a stack overflow event if one occurs unexpectedly in legacy systems.