CVE-2026-41066
HIGHCVE-2026-41066 is a high-severity (CVSS 7.5) vulnerability in lxml. O3 Security confirms whether CVE-2026-41066 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
lxml: Default configuration of iterparse() and ETCompatXMLParser() allows XXE to local files
Real-World Exposure
lxmlReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
lxml is a library for processing XML and HTML in the Python language. Prior to 6.1.0, using either of the two parsers in the default configuration (with resolve_entities=True) allows untrusted XML input to read local files. Setting the resolve_entities option explicitly to resolve_entities='internal' or resolve_entities=False disables the local file access. This vulnerability is fixed in 6.1.0.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | lxml | all versions | 6.1.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for lxml. 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 lxml to 6.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-41066 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-2026-41066 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-2026-41066. 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-2026-41066 in your dependencies?
O3 detects CVE-2026-41066 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.