CVE-2026-33036
A public proof of concept exists; no exploitation attested.
- Published2026-03-20
- Fixed in5.5.6 · 4.5.5
- WeaknessCWE-776
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
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.
Timeline
dates in UTC- 2026-03-2006:16CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-33036?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-33036?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD · OSV| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 5.5 | ≥ 4.0.1, < 5.5.6 | 5.5.6 | NVD |
| 5.x | ≥ 5.0.0, < 5.5.6 | 5.5.6 | OSV |
| 4.x | ≥ 4.0.0-beta.3, < 4.5.5 | 4.5.5 | OSV |
| 4.0 | = 4.0.0 | no fix published | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Distribution builds and vendor advisories
Packages from OSV.dev and products from the vendors' CSAF advisories.
version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.
Vendor advisories
Red Hat Security Advisory: General availability of the satellite/iop-host-inventory-frontend-rhel9 container image
Red Hat Security Advisory: Red Hat OpenShift Data Foundation 4.18.25 security, enhancement & bug fix update
Red Hat Security Advisory: Red Hat OpenShift Data Foundation 4.18.20 security, enhancement & bug fix update
Red Hat Security Advisory: Red Hat OpenShift Data Foundation 4.19.15 security, enhancement & bug fix update
Red Hat Security Advisory: Red Hat Developer Hub 1.8.6 release.
Fix
- Update Naturalintelligence fast-xml-parser to 5.5.6 · 4.5.5
- Vendor fix Red Hat Product Security RHSA-2026:51349 · 1 productFor Red Hat Lightspeed in Satellite installation see the Red Hat Satellite documentation.
- Vendor fix Red Hat Product Security RHSA-2026:41941 · 68 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://docs.redhat.com/en/documentation/red_hat_openshift_data_foundation/4.18/html/updating_openshift_data_foundation/updating-ocs-…
- Vendor fix Red Hat Product Security RHSA-2026:12279 · 78 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://docs.redhat.com/en/documentation/red_hat_openshift_data_foundation/4.19/html/updating_openshift_data_foundation/updating-ocs-…
- Vendor fix Red Hat Product Security RHSA-2026:9742 · 1 productFor more about Red Hat Developer Hub, see References links
- Workaround from the vendor Red Hat Product Security RHSA-2026:51349 · 1 productMitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Advisories and patches
- github.comPatch
- github.comRelease Notes
- github.comMitigation · Vendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Published
- 2026-03-20
- Last Modified
- 2026-06-17
- NVD status
- Analyzed
Frequently asked questions
What is CVE-2026-33036?
Is CVE-2026-33036 actively exploited?
What is the CVSS score for CVE-2026-33036?
Running fast-xml-parser? Hear about its next vulnerability
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.