CVE-2026-33036
7.5 · HIGHOverview
CVE-2026-33036 is a high-severity vulnerability affecting naturalintelligence fast-xml-parser. It was published on March 20, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Versions 4.0.0-beta.3 through 5.5.5 contain a bypass vulnerability where numeric character references (&#NNN;, &#xHH;) and standard XML entities completely evade the entity expansion limits (e.g., maxTotalExpansions, maxExpandedLength) added to fix CVE-2026-26278, enabling XML entity expansion Denial of Service. The root cause is that replaceEntitiesValue() in OrderedObjParser.js only enforces expansion counting on DOCTYPE-defined entities while the lastEntities loop handling numeric/standard entities performs no counting at all. An attacker supplying 1M numeric entity references like A can force ~147MB of memory allocation and heavy CPU usage, potentially crashing the process—even when developers have configured strict limits. This issue has been fixed in version 5.5.6.
Remediation
Check the references section for vendor advisories and patches from naturalintelligence. Update fast-xml-parser to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| naturalintelligence | fast-xml-parser | >= 4.0.1, < 5.5.6 | Affected |
Frequently Asked Questions
What is CVE-2026-33036?
CVE-2026-33036 is a high-severity vulnerability affecting naturalintelligence fast-xml-parser. It was published on March 20, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).
How severe is CVE-2026-33036?
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-33036?
Check the references section for vendor advisories and patches from naturalintelligence. Update fast-xml-parser to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-33036?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-33036 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
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