fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 4.1.3 through 5.3.5, the XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML input, it’s possible to make the parser spend seconds or even minutes processing a single request, effectively freezing the application. Version 5.3.6 fixes the issue. As a workaround, avoid using DOCTYPE parsing by processEntities: false option.
CVE-2026-26278
HIGHPre-NVD 7.57.5
EchelonGraph scoreLOW confidence
This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: secondary
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5(low)
- EPSS
- 52.5%
- KEV
- Not listed
Published
February 19, 2026
Last Modified
July 2, 2026
Advisory Details (10)
Auto-updated Jul 3, 2026🔬 Proof of concept available. Patch available. Sources: github_commit, github_release, github, redhat.
redhat Patch Available
redhat
2441120 – (CVE-2026-26278) CVE-2026-26278 fast-xml-parser: fast-xml-parser: Denial of Service via unlimited XML entity expansion
https://bugzilla.redhat.com/show_bug.cgi?id=2441120redhat Patch Available
redhat Patch Available
redhat Patch Available
redhat Patch Available
github Patch Available🟡 PoC Available
DoS through entity expansion in DOCTYPE (no expansion limit) · Advisory · NaturalIntelligence/fast-xml-parser · GitHub
https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-jmr7-xgp7-cmfjgithub_release Patch Available
Entity security and performance
Patch available: NaturalIntelligence/fast-xml-parser v5.3.6
https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.6github_commit Patch Available
commit 910dae5be2de (NaturalIntelligence/fast-xml-parser)
Patch available: NaturalIntelligence/fast-xml-parser v5.3.6 (contains commit 910dae5be2de)
https://github.com/NaturalIntelligence/fast-xml-parser/commit/910dae5be2de2955e968558fadf6e8f74f117a77Vendor Advisories for CVE-2026-26278(4)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:7128Red Hat Product SecurityHigh
Red Hat Security Advisory: RHACS 4.9.5 security and bug fix update
- RHSA-2026:7110Red Hat Product SecurityHigh
Red Hat Security Advisory: RHACS 4.8.10 security and bug fix update
- RHSA-2026:6802Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Developer Hub 1.9.3 release.
- RHSA-2026:6174Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Developer Hub 1.8.5 release.
Patch Availability(4)
| Vendor / Ecosystem | Fixed in / Patch | Released | Source |
|---|---|---|---|
| redhat | advanced-cluster-security/rhacs-main-rhel8:1775594119 | 2026-04-08 | redhat |
| redhat | advanced-cluster-security/rhacs-main-rhel8:1775594284 | 2026-04-08 | redhat |
| redhat | rhdh/rhdh-hub-rhel9:1775140647 | 2026-04-07 | redhat |
| redhat | rhdh/rhdh-hub-rhel9:1774545605 | 2026-03-30 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(1 across 1 ecosystem)
npm(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| fast-xml-parser | — | 4.5.4 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 11× in last 7d / 14× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-06 16:27 UTCEPSS rescore
- 2026-07-06 16:27 UTCEPSS rescore
- 2026-07-06 02:23 UTCEPSS rescore
- 2026-07-06 02:23 UTCEPSS rescore
- 2026-07-05 02:30 UTCEPSS rescore
- 2026-07-04 06:31 UTCEPSS rescore
- 2026-07-04 06:31 UTCEPSS rescore
- 2026-07-01 15:06 UTCEPSS rescore
- 2026-07-01 15:06 UTCEPSS rescore
- 2026-06-30 23:22 UTCEPSS rescore
- 2026-06-30 23:22 UTCEPSS rescore
- 2026-06-30 04:42 UTCEG score recompute
- 2026-06-30 04:42 UTCVendor advisory
- 2026-06-30 04:31 UTCNVD updatefirst tracked
Frequently asked(5)
What is CVE-2026-26278?
CVE-2026-26278 is a high vulnerability published on February 19, 2026. fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 4.1.3 through 5.3.5, the XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML input, it’s possible to…
When was CVE-2026-26278 disclosed?
CVE-2026-26278 was first published in the National Vulnerability Database on February 19, 2026, with the most recent update on July 2, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-26278 actively exploited?
CVE-2026-26278 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 52.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-26278?
CVE-2026-26278 has a CVSS v4.0 base score of 7.5 (CNA self-assessment; NVD's own analysis pending). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-26278?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-26278, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-26278
Is Your Infrastructure Affected by CVE-2026-26278?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.