CVE-2026-25896 is a critical-severity (CVSS 9.3) CWE-185 vulnerability in fast-xml-parser. A fix is available for fast-xml-parser — see the affected versions and patch details below.
fast-xml-parser has an entity encoding bypass via regex injection in DOCTYPE entity names
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-2026-25896.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-25896 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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.
fast-xml-parsernpmDescription
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. From 4.1.3to before 5.3.5, a dot (.) in a DOCTYPE entity name is treated as a regex wildcard during entity replacement, allowing an attacker to shadow built-in XML entities (<, >, &, ", ') with arbitrary values. This bypasses entity encoding and leads to XSS when parsed output is rendered. This vulnerability is fixed in 5.3.5.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | fast-xml-parser | ≥ 5.0.0&&< 5.3.5 | 5.3.5npm install fast-xml-parser@5.3.5 |
| 📦npm | fast-xml-parser | ≥ 4.1.3&&< 4.5.4 | 4.5.4npm install fast-xml-parser@4.5.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fast-xml-parser, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update fast-xml-parser to 5.3.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-25896 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-25896 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-25896. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This flaw has been assessed as IMPORTANT for Red Hat products. This vulnerability arises when the parsed XML output is subsequently rendered to users which requires the interaction of the user. The impact of this flaw is also limited to the user's browser context.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Advanced Cluster Security 4.8 | advanced-cluster-security/rhacs-main-rhel8:1775594119 | RHSA-2026:7110 |
| Red Hat Advanced Cluster Security 4.9 | advanced-cluster-security/rhacs-main-rhel8:1775594284 | RHSA-2026:7128 |
| Red Hat Developer Hub 1.8 | rhdh/rhdh-hub-rhel9:1774545605 | RHSA-2026:6174 |
| Red Hat Developer Hub 1.9 | rhdh/rhdh-hub-rhel9:1775140647 | RHSA-2026:6802 |
| Red Hat Openshift Data Foundation 4.18 | odf4/cephcsi-rhel9:1783676191 | RHSA-2026:41941 |
| Red Hat Openshift Data Foundation 4.19 | odf4/cephcsi-rhel9:1783684360 | RHSA-2026:41944 |
| Red Hat Openshift Data Foundation 4.20 | odf4/cephcsi-rhel9:1783667125 | RHSA-2026:40984 |
| Red Hat Satellite 6.18 | satellite/iop-host-inventory-frontend-rhel9:1785922764 | RHSA-2026:51349 |
Frequently Asked Questions
Is CVE-2026-25896 in your dependencies?
O3 Security finds CVE-2026-25896 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.