xmldom Uncontrolled Recursion DoS Vulnerability

hello@craftedsignal.io — Thu, 23 Apr 2026 12:00:00 +0000

The xmldom library is susceptible to a denial-of-service (DoS) vulnerability due to uncontrolled recursion in XML serialization. Seven recursive traversals within lib/dom.js lack depth limits, causing a RangeError: Maximum call stack size exceeded and crashing the application when processing deeply nested XML documents. Publicly disclosed on 2026-04-06, the vulnerability impacts multiple functions, including normalize(), XMLSerializer.serializeToString(), and others related to DOM manipulation. This issue arises from the library’s pure-JavaScript recursive implementation of DOM operations, which exhausts the call stack. Exploitation requires no authentication or special options, affecting applications that process attacker-controlled XML using vulnerable xmldom versions ( < 0.8.13, >= 0.9.0 and < 0.9.10, and <= 0.6.0).

Attack Chain

An attacker crafts a malicious XML document with deeply nested elements.
The vulnerable application receives and parses the crafted XML document using DOMParser.parseFromString().
The application subsequently calls one of the affected DOM operations, such as normalize(), serializeToString(), getElementsByTagName(), or cloneNode(true).
The affected function initiates a recursive traversal of the deeply nested XML structure within lib/dom.js.
Each level of nesting consumes a JavaScript call stack frame.
The recursive calls continue until the JavaScript engine’s call stack is exhausted.
A RangeError: Maximum call stack size exceeded exception is thrown.
The application crashes due to the uncaught exception, leading to a denial of service.

Impact

Successful exploitation results in a denial-of-service condition. Any service parsing attacker-controlled XML with a vulnerable version of xmldom can be crashed by a single crafted payload. This can lead to failed request processing. In deployments where uncaught exceptions terminate the worker or process, the impact can extend beyond a single request and disrupt service availability more broadly. Tests show that stack exhaustion occurs with nesting depths between 5,000 and 10,000 levels depending on the operation.

Recommendation

Upgrade @xmldom/xmldom to version >= 0.8.13 or >= 0.9.10 to remediate CVE-2026-41673.
If upgrading is not immediately feasible, consider implementing input validation to limit the nesting depth of XML documents processed by applications using xmldom.
Monitor application logs for RangeError: Maximum call stack size exceeded exceptions originating from lib/dom.js, which could indicate exploitation attempts.

xmldom XML Injection Vulnerability

hello@craftedsignal.io — Wed, 03 Jan 2024 12:00:00 +0000

The @xmldom/xmldom and xmldom packages are vulnerable to XML injection due to the lack of validation when serializing DocumentType node fields. Specifically, the internalSubset, publicId, and systemId fields are serialized verbatim without any escaping or validation. This vulnerability affects @xmldom/xmldom versions prior to 0.8.13 and versions 0.9.0 to 0.9.9, as well as xmldom versions up to 0.6.0. The vulnerability is triggered when these fields are programmatically set to attacker-controlled strings, leading to potential arbitrary markup injection outside the DOCTYPE declaration during serialization using XMLSerializer.serializeToString. This can lead to downstream XML parsers being susceptible to XXE attacks. Defenders should audit serializeToString() call sites and add { requireWellFormed: true } to mitigate this vulnerability.

Attack Chain

The attacker identifies an application using a vulnerable version of @xmldom/xmldom or xmldom.
The attacker finds a code path where they can control the publicId, systemId, or internalSubset properties of a DocumentType node.
The attacker crafts a malicious string containing XML injection payloads (e.g., closing DOCTYPE tags or injecting SYSTEM entities).
The attacker uses programmatic calls to createDocumentType or direct property writes to set the malicious string as the value of the publicId, systemId, or internalSubset field.
The application calls XMLSerializer.serializeToString on the document, without the { requireWellFormed: true } option.
The vulnerable serializer emits a DOCTYPE declaration where the injected malicious string is included verbatim, causing the DOCTYPE declaration to be terminated early or to include injected entities.
The serialized XML is passed to a downstream XML parser that performs entity expansion.
The downstream XML parser expands the injected entities, leading to potential XXE attacks, information disclosure, or other malicious actions.

Impact

Successful exploitation of this vulnerability can lead to the injection of arbitrary XML markup, potentially enabling XXE attacks against downstream XML parsers. The impact includes potential information disclosure, arbitrary code execution, or denial-of-service if the downstream parser expands external entities. This vulnerability impacts applications using vulnerable versions of @xmldom/xmldom and xmldom that construct DocumentType nodes from user-controlled data and serialize the document without proper validation.

Recommendation

Upgrade to @xmldom/xmldom version 0.8.13 or later, or version 0.9.10 or later, to receive the fix.
Upgrade to a version of xmldom greater than 0.6.0.
Audit all calls to XMLSerializer.serializeToString() and add the option { requireWellFormed: true } to enforce validation of DocumentType node fields, as described in the advisory.
Applications that pass untrusted data to createDocumentType() or write untrusted values directly to a DocumentType node’s publicId, systemId, or internalSubset properties should audit all serializeToString() call sites and add the option.

Xmldom — CraftedSignal Threat Feed

xmldom Uncontrolled Recursion DoS Vulnerability

Attack Chain

Impact

Recommendation

xmldom XML Injection Vulnerability

Attack Chain

Impact

Recommendation