# CVE-2026-83618: xmldom: requireWellFormed DocType publicId/systemId validation is bypassable via an embedded line terminator

> Attackers can bypass XML serialization validation to inject malicious markup, potentially leading to 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:** 4 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-83618, GHSA-vr34-hp96-76pp, ROOT-APP-NPM-CVE-2026-83618, UBUNTU-CVE-2026-83618

## What is CVE-2026-83618?

CVE-2026-83618 is a high-severity code injection 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 0.9.10 until 0.9.12, the requireWellFormed: true serializer validates DocumentType.publicId and DocumentType.systemId with PubidLiteral_match and SystemLiteral_match expressions produced by reg() in lib/grammar.js, which inherit the multiline flag. A complete valid literal on the first line can therefore satisfy the matcher while U+000A, U+000D, U+2028, or U+2029 and breakout markup remain in the emitted <!DOCTYPE ...> declaration. This bypasses the strict-serialization mitigation for the earlier DocumentType injection advisory; creation and direct property assignment remain unvalidated by design. 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-2026-83618?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@xmldom/xmldom` | npm | From 0.9.10 | 0.9.12 |
| `@xmldom/xmldom` | npm | From 0.9.10 | 0.9.12 |

## How do I fix CVE-2026-83618?

Upgrade @xmldom/xmldom to 0.9.12 or later.

## Is CVE-2026-83618 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-83618 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-83618 and fix it if it is affected.

What it is: CVE-2026-83618 is a high-severity code injection 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-83618 exists.

Affected packages and fixed versions:
- @xmldom/xmldom (npm): affected from 0.9.10; fixed in 0.9.12
- @xmldom/xmldom (npm): affected from 0.9.10; 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-2026-83618/ (Markdown: https://insights.sbomify.com/CVE-2026-83618/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-83618
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-83618
- OSV: https://osv.dev/vulnerability/CVE-2026-83618

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-83618/
Summaries are generated and may contain mistakes; the official description above is the record.