How severe is CVE-2021-33611?

CVE-2021-33611 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-2021-33611?

CVE-2021-33611 affects the following packages: com.vaadin:vaadin-bom (Maven), org.webjars.bowergithub.vaadin:vaadin-menu-bar (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-33611?

Update com.vaadin:vaadin-bom to 14.4.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-33611 is resolved across your whole dependency graph.

How do I detect CVE-2021-33611 in my Maven dependencies?

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

How do I mitigate CVE-2021-33611 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-2021-33611 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-33611, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-33611?

CVE-2021-33611 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 61th 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-2021-33611?

CVE-2021-33611 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type 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-2021-33611 published, and has it been updated?

CVE-2021-33611 was published on November 2, 2021 and was last updated on July 8, 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-2021-33611 — vaadin-bom

MEDIUMFix: vaadin/vaadin-menu-bar#126

CVE-2021-33611 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in com.vaadin:vaadin-bom. 1 public exploit reference exists, so weaponization risk is real. A fix is available for com.vaadin:vaadin-bom — see the affected versions and patch details below.

Reflected cross-site scripting in vaadin-menu-bar webjar resources in Vaadin 14

Also known asGHSA-93c4-vf86-3rj7

Published

Nov 2, 2021

Updated

Jul 8, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

1 known

Exploitation data as of Oct 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs61th percentile — riskier than 61% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2021-33611 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 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:vaadin-bom☕org.webjars.bowergithub.vaadin:vaadin-menu-bar

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 test sources in org.webjars.bowergithub.vaadin:vaadin-menu-bar versions 1.0.0 through 1.2.0 (Vaadin 14.0.0 through 14.4.4) allows remote attackers to execute malicious JavaScript in browser by opening crafted URL

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`com.vaadin:vaadin-bom`	≥ 14.0.0&&< 14.4.5	14.4.5`com.vaadin:vaadin-bom:14.4.5`
☕Maven	`org.webjars.bowergithub.vaadin:vaadin-menu-bar`	≥ 1.0.0&&< 1.2.1	1.2.1`org.webjars.bowergithub.vaadin:vaadin-menu-bar:1.2.1`

Affected Products

2 products · 2 configurations

Application

vaadinvaadin

≥ 14.0.0 && ≤ 14.4.4

range

Application

vaadin-menu-barvaadin

≥ 1.0.0 && ≤ 1.2.0

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Missing output sanitization in test sources in org.webjars.bowergithub.v…

vaadin.comNVDNov 2021

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:vaadin-bom, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update com.vaadin:vaadin-bom to 14.4.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-33611 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

O3 Security · Impact-Aware SCA

Is CVE-2021-33611 in your dependencies?

Find it across Maven, including transitive dependencies.

Scan my dependencies How O3 SCA works

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-79Cross-site Scripting (XSS)

Weaponization

No known public exploit tooling found.

OpenSSF Scorecard

Package health score

vaadin-menu-bar

4.3/10

Code-Review4/10

Maintained0/10

Branch-ProtectionN/A

Assessed Oct 5, 2026

Timeline

Disclosed

Nov 2, 2021

First exploit

Nov 2, 2021

1 day after disclosure — rapid exploitation

Last updated

Jul 8, 2026

Identifiers

CVE-2021-33611

GHSA-93c4-vf86-3rj7

References

Advisorynvd.nist.gov Fixgithub.com Webgithub.com Packagegithub.com Evidencevaadin.com

Related vulnerabilities

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

GHSA-jfmf-w293-8xr8GHSA-hw7r-qrhp-5pffCVE-2021-33604CVE-2021-31412CVE-2021-31411CVE-2021-31408CVE-2021-31405GHSA-3h5r-928v-mxhh

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedJul 8, 2026

CVE-2021-33611 — vaadin-bom

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2021-33611 in your dependencies?