# CVE-2026-83609: xmldom: Creation-time XML Name/QName validation is bypassable via an embedded line terminator, allowing injection on the default serialization path

> Attackers can inject malicious markup into XML documents via line terminators in names, leading to potential XSS or code execution in applications using xmldom.

- **Severity:** High 8.7 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 Sep 2026
- **Updated:** 1 Sep 2026
- **Also known as:** CLSA-2026-1793108546, DEBIAN-CVE-2026-83609, GHSA-3px3-54cx-rmw9, ROOT-APP-NPM-CVE-2026-83609, UBUNTU-CVE-2026-83609

## What is CVE-2026-83609?

CVE-2026-83609 is a high-severity cross-site scripting vulnerability in @xmldom xmldom, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. From 0.9.0 until 0.9.12, the shared reg() builder in lib/grammar.js compiles the anchored QName_exact validator with the multiline flag, so ^ and $ validate only one line instead of the complete name. createElementNS, createAttributeNS, createDocumentType, and createAttribute consequently accept a malformed XML name whose first line is valid and whose later text injects markup when serialized through either the default path or requireWellFormed: true. The triggering ECMAScript line terminators are U+000A, U+000D, U+2028, and U+2029. This issue is fixed in @xmldom/xmldom version 0.9.12.

Weakness: CWE-91 (XML Injection), CWE-625 (Permissive Regular Expression)

## Which versions are affected by CVE-2026-83609?

2 open source packages ship an affected version, including @xmldom/xmldom.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@xmldom/xmldom` | npm | From 0.9.0 | 0.9.12 |
| `@xmldom/xmldom` | npm | From 0.9.0 | 0.9.12 |

## How do I fix CVE-2026-83609?

Upgrade @xmldom/xmldom to 0.9.12 or later.

## Is CVE-2026-83609 being exploited?

There is no known exploitation of CVE-2026-83609 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-83609 and fix it if it is affected.

What it is: CVE-2026-83609 is a high-severity cross-site scripting vulnerability in @xmldom xmldom, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-83609 in the wild and no public exploit code.

Affected packages and fixed versions:
- @xmldom/xmldom (npm): affected from 0.9.0; fixed in 0.9.12
- @xmldom/xmldom (npm): affected from 0.9.0; fixed in 0.9.12

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-83609/ (Markdown: https://insights.sbomify.com/CVE-2026-83609/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-83609
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-83609
- OSV: https://osv.dev/vulnerability/CVE-2026-83609

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-83609/
Summaries are generated and may contain mistakes; the official description above is the record.