CVE-2026-83611
Fix: xmldom/xmldom@4430189CVE-2026-83611 is a CWE-1286 vulnerability in @xmldom/xmldom. O3 Security confirms whether CVE-2026-83611 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
xmldom: Parser silently accepts a not-well-formed end tag whose name is followed by a line break and trailing content
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-83611.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@xmldom/xmldomnpmxmldomnpmDescription
xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom version 0.6.0 and earlier, DOMParser.parseFromString() can silently accept an end tag such as </a\njunk>, close the element, and discard the trailing content. On 0.9.x, the lib/sax.js end-tag validator inherits the multiline flag from reg(), allowing the first line to satisfy the anchored XML ETag production; older lines have no equivalent residue validation. This parser differential can bypass a parse-before-trust well-formedness gate, although it does not inject the discarded content; onError on 0.9.x and errorHandler on 0.8.x are the relevant reporting interfaces. This issue is fixed in @xmldom/xmldom versions 0.8.15 and 0.9.12; no fixed version is available for xmldom.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @xmldom/xmldom | ≥ 0.7.0&&< 0.8.15 | 0.8.15 |
| 📦npm | @xmldom/xmldom | ≥ 0.9.0&&< 0.9.12 | 0.9.12 |
| 📦npm | xmldom | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @xmldom/xmldom. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @xmldom/xmldom to 0.8.15 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-83611 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-83611 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-83611. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-83611 in your dependencies?
O3 detects CVE-2026-83611 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.