VulnerabilityPublished 22 Apr 2026Updated 8 May 2026

CVE-2026-41672: @xmldom/xmldom · xmldom has XML node injection through unvalidated comment serialization

Affects @xmldom/xmldomSource GCVE Database

Not known to be exploited · CVSS 8.7 High : upgrade to 0.8.13 soon.

Data as of 27 Oct 2026, 00:07 UTC

CVSS 4.0 base score

8.7High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 0.8.13, 0.9.10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: High
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade @xmldom/xmldom to 0.8.13; @xmldom/xmldom to 0.9.10.

Affected software

Product	Affected	Fixed in
npm@xmldom/xmldom	Affected <0.8.13	Fixed in 0.8.13
npm@xmldom/xmldom	Affected >=0.9.0 <0.9.10	Fixed in 0.9.10
npmxmldom	Affected <=0.6.0	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

## Summary The package allows attacker-controlled comment content to be serialized into XML without validating or neutralizing comment breaking sequences. As a result, an attacker can terminate the comment early and inject arbitrary XML nodes into the serialized output. --- ## Details The issue is in the DOM construction and serialization flow for comment nodes. When `createComment(data)` is called, the supplied string is stored as comment data through the generic character-data handling path. That content is kept as-is. Later, when the document is serialized, the serializer writes comment nodes by concatenating the XML comment delimiters with the stored `node.data` value directly. That behavior is unsafe because XML comments are a syntax-sensitive context. If attacker-controlled input contains a sequence that closes the comment, the serializer does not preserve it as literal comment text. Instead, it emits output where the remainder of the payload is treated as live XML markup. This is a real injection bug, not a formatting issue. The serializer already applies context-aware handling in other places, such as escaping text nodes and rewriting unsafe CDATA terminators. Comment content does not receive equivalent treatment. Because of that gap, untrusted data can break out of the comment boundary and modify the structure of the final XML document. --- ## PoC ```js const { DOMImplementation, DOMParser, XMLSerializer } = require('@xmldom/xmldom'); const doc = new DOMImplementation().createDocument(null, 'root', null); doc.documentElement.appendChild( doc.createComment('--><injected attr="1"/><injected attr="1"/></root> const reparsed = new DOMParser().parseFromString(xml, 'text/xml'); console.log(reparsed.documentElement.childNodes.item(1).nodeName); // injected ``` --- ## Impact An application that uses the package to build XML from untrusted input can be made to emit attacker-controlled elements outside the intended comment boundary. That allows the attacker to alter the meaning and structure of generated XML documents. In practice, this can affect any workflow that generates XML and then stores it, forwards it, signs it, or hands it to another parser. Realistic targets include XML-based configuration, policy documents, and message formats where downstream consumers trust the serialized structure. --- ## Disclosure This vulnerability was publicly disclosed at 2026-04-06T11:25:07Z via [xmldom/xmldom#987](https://github.com/xmldom/xmldom/pull/987), which was subsequently closed without being merged. --- ## Fix Applied > **⚠ Opt-in required.** Protection is not automatic. Existing serialization calls remain > vulnerable unless `{ requireWellFormed: true }` is explicitly passed. Applications that pass > untrusted data to `createComment()` or mutate comment nodes with untrusted input (via > `appendData`, `insertData`, `replaceData`, `.data =`, or `.textContent =`) should audit all > `serializeToString()` call sites and add the option. `XMLSerializer.serializeToString()` now accepts an options object as a second argument. When `{ requireWellFormed: true }` is passed, the serializer throws `InvalidStateError` before emitting a Comment node whose `.data` would produce malformed XML. On `@xmldom/xmldom` ≥ 0.9.10, the full W3C DOM Parsing §3.2.1.4 check is applied: throws if `.data` contains `--` anywhere, ends with `-`, or contains characters outside the XML Char production. On `@xmldom/xmldom` ≥ 0.8.13 (LTS), only the `-->` injection sequence is checked. The `0.8.x` SAX parser accepts comments containing `--` (without `>`), so throwing on bare `--` would break a previously-working round-trip on that branch. The `-->` check is sufficient to prevent injection. ### PoC — fixed path ```js const { DOMImplementation, XMLSerializer } = require('@xmldom/xmldom'); const doc = new DOMImplementation().createDocument(null, 'root', null); doc.documentElement.appendChild(doc.createComment('--><injected attr="1"/><injected attr="1"/></root> // Opt-in guard: throws InvalidStateError before serializing try { new XMLSerializer().serializeToString(doc, { requireWellFormed: true }); } catch (e) { console.log(e.name, e.message); // InvalidStateError: The comment node data contains "--" or ends with "-" (0.9.x) // InvalidStateError: The comment node data contains "-->" (0.8.x — only --> is checked) } ``` ### Why the default stays verbatim The W3C DOM Parsing and Serialization spec §3.2.1.4 defines a `require well-formed` flag whose **default value is `false`**. With the flag unset, the spec explicitly permits serializing ill-formed comment content verbatim — this is also the behavior of browser implementations (Chrome, Firefox

CWE-91XML Injection (aka Blind XPath Injection) (opens in a new tab)
Base weaknessOWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not properly neutralize special elements that are used in XML, allowing attackers to modify the syntax, content, or commands of the XML before it is processed by an end system.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
Injection Prevention (opens in a new tab)
SQL Injection Prevention (opens in a new tab)
Injection Prevention in Java (opens in a new tab)
OWASP ASVS 4.0.3
V1.5.1 (opens in a new tab)
Attack patterns
XML Injection (opens in a new tab)
XPath Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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What to do

Affected software

Description

WeaknessesCWE-91

Technical details

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