How severe is CVE-2019-25027?

CVE-2019-25027 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2019-25027?

CVE-2019-25027 affects the following packages: com.vaadin:flow-server (Maven), com.vaadin:flow-server (Maven). Ecosystems affected: Maven.

How do I fix CVE-2019-25027?

Update com.vaadin:flow-server to 1.0.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-25027 is resolved across your whole dependency graph.

How do I detect CVE-2019-25027 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for com.vaadin:flow-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2019-25027 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2019-25027 actively exploited in the wild?

No public exploit code has been indexed for CVE-2019-25027 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2019-25027?

CVE-2019-25027 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 51th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2019-25027?

CVE-2019-25027 is classified as CWE-81 (CWE-81), Cross-site Scripting (XSS) (CWE-79). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2019-25027 published, and has it been updated?

CVE-2019-25027 was published on April 23, 2021 and was last updated on August 7, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

MEDIUM severity

CVE-2019-25027 — flow-server

MEDIUMFix: vaadin/flow#5498

CVE-2019-25027 is a medium-severity (CVSS 6.1) CWE-81 vulnerability in com.vaadin:flow-server. A fix is available for com.vaadin:flow-server — see the affected versions and patch details below.

Reflected cross-site scripting in default RouteNotFoundError view in Vaadin 10 and 11-13

Also known asGHSA-rp4x-wxqv-cf9m

Published

Apr 23, 2021

Updated

Aug 7, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs51th percentile — riskier than 51% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2019-25027 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected

☕com.vaadin:flow-server☕com.vaadin:flow-server

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Missing output sanitization in default RouteNotFoundError view in com.vaadin:flow-server versions 1.0.0 through 1.0.10 (Vaadin 10.0.0 through 10.0.13), and 1.1.0 through 1.4.2 (Vaadin 11.0.0 through 13.0.5) allows attacker to execute malicious JavaScript via crafted URL.

https://vaadin.com/security/cve-2019-25027

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`com.vaadin:flow-server`	≥ 1.0.0&&< 1.0.11	1.0.11`com.vaadin:flow-server:1.0.11`
☕Maven	`com.vaadin:flow-server`	≥ 1.1.0&&< 1.4.3	1.4.3`com.vaadin:flow-server:1.4.3`

Affected Products

2 products · 4 configurations

Application

flowvaadin

≥ 1.1.0 && < 1.4.3

range

Application

vaadinvaadin

≥ 11.0.0 && < 13.0.6

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for com.vaadin:flow-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update com.vaadin:flow-server to 1.0.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-25027 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

Missing output sanitization in default `RouteNotFoundError` view in `com.vaadin:flow-server` versions 1.0.0 through 1.0.10 (Vaadin 10.0.0 through 10.0.13), and 1.1.0 through 1.4.2 (Vaadin 11.0.0 through 13.0.5) allows attacker to execute malicious JavaScript via crafted URL. - https://vaadin.com/security/cve-2019-25027

O3 Security · Impact-Aware SCA

Is CVE-2019-25027 in your dependencies?

Find it across Maven, including transitive dependencies.

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CVSS Score

6.1/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CWE Classification

CWE-81CWE-81 CWE-79Cross-site Scripting (XSS)

Weaponization

No known public exploit tooling found.

OpenSSF Scorecard

Package health score

flow

5.5/10

Code-Review10/10

Maintained10/10

Branch-Protection4/10

Assessed Oct 19, 2026

Timeline

Disclosed

Apr 23, 2021

Last updated

Aug 7, 2026

Identifiers

CVE-2019-25027

GHSA-rp4x-wxqv-cf9m

References

Advisoryvaadin.com Advisorynvd.nist.gov Fixgithub.com Webgithub.com

Related vulnerabilities

This CVE is medium severity; 6 of 8 other CVEs affecting flow-server are rated as high or higher (top: high).

CVE-2026-2742CVE-2023-25499CVE-2023-25500GHSA-fr26-qjc8-mvjxGHSA-8vfw-v2jv-9hwcGHSA-c57f-4vp2-jqhmCVE-2021-31407CVE-2020-36321

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedAug 7, 2026