CVE-2026-83612 xmldom: HTML raw-text closing-tag case mismatch causes output amplification
Attackers can cause excessive CPU and memory consumption by providing malformed HTML to the xmldom parser, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-83612?
CVE-2026-83612 is a high-severity denial of service 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-beta.1 until 0.9.12, HTML-mode parsing through DOMParser.parseFromString() mishandles a mixed-case closing tag for the script, style, textarea, or title raw-text elements. parseHtmlSpecialContent, selected by isHTMLRawTextElement or isHTMLEscapableRawTextElement, uses a case-sensitive indexOf() and then calls substring() with a missing-close result of negative one, causing unstable parser progression and quadratic output amplification. A small untrusted text/html document can consequently consume disproportionate CPU and memory when parsed and serialized. This issue is fixed in @xmldom/xmldom version 0.9.12.
Which versions are affected by CVE-2026-83612?
2 open source packages ship an affected version, including @xmldom/xmldom.
| Package | Affected | Fixed in |
|---|---|---|
@xmldom/xmldom npm | From 0.9.0-beta.1 | 0.9.12 |
@xmldom/xmldom npm | From 0.9.0-beta.1 | 0.9.12 |
How do I fix CVE-2026-83612?
Upgrade @xmldom/xmldom to 0.9.12 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-83612 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-83612 exists.
Sources
Also known as CLSA-2026-1791571542, DEBIAN-CVE-2026-83612, GHSA-6mj3-qw4j-hgrw, ROOT-APP-NPM-CVE-2026-83612, UBUNTU-CVE-2026-83612.