# CVE-2026-83617: xmldom: requireWellFormed element/attribute name validation is bypassable via an embedded line terminator

> Attackers can bypass XML well-formedness checks to inject markup, potentially leading to code execution or security bypasses 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:** DEBIAN-CVE-2026-83617, GHSA-jxjr-3g7g-3944, ROOT-APP-NPM-CVE-2026-83617, UBUNTU-CVE-2026-83617

## What is CVE-2026-83617?

CVE-2026-83617 is a high-severity 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 0.9.11 until 0.9.12, the requireWellFormed: true element and attribute name checks use the anchored QName_exact expression produced by reg() in lib/grammar.js, which inherits the multiline flag. A name with a valid first line followed by U+000A, U+000D, U+2028, or U+2029 and breakout markup therefore passes validation and is emitted verbatim in element start and end tags or attribute names. This bypasses the strict-serialization checks introduced for the earlier element-name and attribute-name injection advisories, while the default serialization path remains outside the strict guarantee. 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-2026-83617?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@xmldom/xmldom` | npm | From 0.9.11 | 0.9.12 |
| `@xmldom/xmldom` | npm | From 0.9.11 | 0.9.12 |

## How do I fix CVE-2026-83617?

Upgrade @xmldom/xmldom to 0.9.12 or later.

## Is CVE-2026-83617 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-83617 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-83617 and fix it if it is affected.

What it is: CVE-2026-83617 is a high-severity 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-2026-83617 exists.

Affected packages and fixed versions:
- @xmldom/xmldom (npm): affected from 0.9.11; fixed in 0.9.12
- @xmldom/xmldom (npm): affected from 0.9.11; 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-2026-83617/ (Markdown: https://insights.sbomify.com/CVE-2026-83617/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-83617
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-83617
- OSV: https://osv.dev/vulnerability/CVE-2026-83617

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-83617/
Summaries are generated and may contain mistakes; the official description above is the record.