CVE-2026-87908 in multiparty
Summary
by MITRE • 09/11/2026
multiparty is a Node.js library for parsing multipart/form-data request bodies. In versions from 2.1.0 up to but not including 4.3.1, the parser does not bound the amount of memory used while accumulating the headers of a single multipart part. An unauthenticated attacker can send a single request whose part carries a very large volume of header bytes, forcing the parser to buffer all of them and exhausting the process memory, which crashes the server. This is a denial of service with no confidentiality or integrity impact. The issue is fixed in multiparty 4.3.1, which caps the size of the accumulated part headers. Users should upgrade to multiparty 4.3.1 or later.
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Analysis
by VulDB Data Team • 09/11/2026
The vulnerability identified within the Node.js library known as multiparty represents a significant resource exhaustion flaw affecting versions ranging from 2.1.0 up to, but not including, version 4.3.1. Multiparty is widely utilized in web application development for parsing multipart/form-data request bodies, which are commonly encountered during file uploads and complex form submissions. The core technical deficiency lies in the parser's handling of header accumulation for individual parts within a multipart message. Specifically, the implementation fails to impose any upper bound on the amount of memory allocated while buffering these headers. This lack of constraint allows an attacker to craft a malicious request containing a single part with an excessively large volume of header bytes. When such a payload is processed by the vulnerable parser, it attempts to buffer all incoming header data into memory without checking against any predefined limits or thresholds designed to prevent excessive consumption.
From an operational perspective, this flaw leads directly to a denial of service condition characterized by resource exhaustion. As the server processes the malicious request, the unbounded accumulation of header bytes causes the Node.js process to consume increasing amounts of system RAM. Since JavaScript engines and Node.js applications typically operate within limited memory spaces defined by their execution environment or container limits, this rapid consumption quickly leads to an out-of-memory state. Consequently, the application crashes or becomes unresponsive, effectively denying service to legitimate users who rely on the same server instance. It is critical to note that this vulnerability impacts availability exclusively; there are no implications for data confidentiality or integrity because the attacker cannot execute arbitrary code, read sensitive information beyond what might be exposed by a crash log, or alter stored data through this specific mechanism. The impact is strictly limited to service disruption via memory exhaustion.
This type of flaw aligns with Common Weakness Enumeration (CWE) category CWE-400, which describes Uncontrolled Resource Consumption. In the context of network-based attacks and adversary tactics, this vulnerability maps closely to techniques found in the MITRE ATT&CK framework under resource hijacking or denial of service vectors where attackers aim to degrade system performance by consuming computational resources such as memory or CPU cycles. The absence of input validation regarding header size is a classic example of insufficient boundary checks that allows external inputs to drive internal state into an unsustainable condition.
To mitigate this vulnerability, organizations must ensure that all instances of the multiparty library are upgraded to version 4.3.1 or any later release where the issue has been resolved. The fix implemented in these newer versions introduces a cap on the size of accumulated part headers, thereby preventing the parser from allocating unbounded memory regardless of the input volume. For environments where immediate upgrading is not feasible due to dependency constraints, temporary mitigations should be considered at the infrastructure level. This includes configuring reverse proxies or web application firewalls to limit the maximum allowed header sizes for incoming requests and enforcing strict timeouts on connection processing times. Additionally, implementing resource limits within the Node.js process itself using operating system-level controls can help contain the impact of such attacks by killing processes that exceed predefined memory thresholds before they bring down the entire server instance.