CVE-2026-83615 in xmldom
Summary
by MITRE • 09/01/2026
xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom versions 0.1.5 through 0.6.0, appendElement in lib/sax.js uses _copy to clone the complete currentNSMap for each nested element that declares a new namespace prefix. Keeping every ancestor map live on the parse stack creates quadratic peak namespace-map storage, so a small highly compressible XML document can exhaust the process heap before application validation. This issue is fixed in @xmldom/xmldom versions 0.8.15 and 0.9.12; no fixed version is available for xmldom.
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Analysis
by VulDB Data Team • 09/01/2026
The vulnerability identified within the xmldom library, a pure JavaScript implementation of the W3C XML DOM Level 2 Core standard, represents a significant resource exhaustion risk stemming from inefficient memory management during XML parsing operations. The core technical flaw resides in the appendElement function located within the lib/sax.js module. When processing an XML document that declares new namespace prefixes for nested elements, this function invokes a _copy method to clone the entire currentNSMap object. This cloning process is executed recursively for every level of nesting where a new namespace prefix is introduced, resulting in the retention of complete ancestor maps on the parse stack rather than discarding or optimizing them as they become less relevant to subsequent parsing steps.
This architectural decision leads to quadratic peak memory consumption relative to the depth and complexity of nested namespaces within the input document. Although XML documents are often highly compressible and may appear small in terms of byte size, the internal representation required by this flawed logic causes exponential growth in heap usage as nesting increases. An attacker can exploit this behavior by crafting a specifically designed malicious XML payload that contains deeply nested elements with unique namespace declarations at each level. Upon processing such a document, the application will rapidly consume available memory resources, leading to process termination or system instability due to out-of-memory conditions before any meaningful application-level validation or business logic can be executed.
From an operational perspective, this vulnerability constitutes a Denial of Service attack vector that targets the availability component of the CIA triad. Because xmldom is frequently utilized in Node.js environments for server-side XML processing, applications relying on this library are susceptible to remote exploitation if they accept untrusted or semi-trusted XML input without prior size constraints or depth limits. The impact extends beyond simple application crashes; it can lead to cascading failures in microservices architectures where a single overloaded node may trigger timeouts or resource starvation across dependent services. Furthermore, the lack of fixed versions for older releases like xmldom 0.1.5 through 0.6.0 necessitates that organizations using these legacy packages implement external mitigations such as input validation wrappers, strict depth limits on XML parsers, or migration to alternative libraries with more robust memory management practices.
This issue aligns with CWE-787: Out-of-bounds Write and CWE-400: Uncontrolled Resource Consumption, specifically highlighting how improper resource allocation during parsing can lead to system instability. In the context of the MITRE ATT&CK framework, this vulnerability facilitates the T1496: Resource Hijacking technique, where attackers leverage computational resources for disruptive purposes rather than malicious data exfiltration or persistence. To mitigate these risks, developers should ensure they are using patched versions such as @xmldom/xmldom 0.8.15 or higher if possible. For environments constrained to older xmldom releases, implementing a custom parser wrapper that enforces maximum namespace depth limits and monitoring heap usage during parsing operations can provide essential protection against exploitation until an upgrade is feasible.