How severe is CVE-2021-31407?

CVE-2021-31407 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-31407?

CVE-2021-31407 affects the following packages: com.vaadin:flow-server (Maven), com.vaadin:flow-server (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-31407?

Update com.vaadin:flow-server to 2.4.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-31407 is resolved across your whole dependency graph.

How do I detect CVE-2021-31407 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-2021-31407 if there is no patch (or I can't update yet)?

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.

Is CVE-2021-31407 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-31407 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-2021-31407?

CVE-2021-31407 has an EPSS (Exploit Prediction Scoring System) score of 2.4%, placing it in the 84th 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-2021-31407?

CVE-2021-31407 is classified as CWE-402 (CWE-402), CWE-668 (CWE-668). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-31407 published, and has it been updated?

CVE-2021-31407 was published on April 23, 2021 and was last updated on October 24, 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

HIGH severity

CVE-2021-31407 — flow-server

HIGHFix: vaadin/flow#10229

CVE-2021-31407 is a high-severity (CVSS 7.5) CWE-402 vulnerability in com.vaadin:flow-server. A fix is available for com.vaadin:flow-server — see the affected versions and patch details below.

OSGi applications using Vaadin 12-14 and 19 vulnerable to server classes and resources exposure

Also known asGHSA-25xc-jwfq-39jw

Published

Apr 23, 2021

Updated

Oct 24, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 24, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

2.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs84th percentile — riskier than 84% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2021-31407 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,492 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

Vulnerability in OSGi integration in com.vaadin:flow-server versions 1.2.0 through 2.4.7 (Vaadin 12.0.0 through 14.4.9), and 6.0.0 through 6.0.1 (Vaadin 19.0.0) allows attacker to access application classes and resources on the server via crafted HTTP request.

https://vaadin.com/security/cve-2021-31407

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`com.vaadin:flow-server`	≥ 1.2.0&&< 2.4.8	2.4.8`com.vaadin:flow-server:2.4.8`
☕Maven	`com.vaadin:flow-server`	≥ 6.0.0&&< 6.0.1	6.0.1`com.vaadin:flow-server:6.0.1`

Affected Products

2 products · 4 configurations

Application

flowvaadin

≥ 6.0.0 && < 6.0.2

range

Application

vaadinvaadin

≥ 12.0.0 && < 14.4.10

1 version

19.0.0

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 2.4.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-31407 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.

Frequently Asked Questions

Vulnerability in OSGi integration in `com.vaadin:flow-server` versions 1.2.0 through 2.4.7 (Vaadin 12.0.0 through 14.4.9), and 6.0.0 through 6.0.1 (Vaadin 19.0.0) allows attacker to access application classes and resources on the server via crafted HTTP request. - https://vaadin.com/security/cve-2021-31407

O3 Security · Impact-Aware SCA

Is CVE-2021-31407 in your dependencies?

Find it across Maven, including transitive dependencies.

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CVSS Score

7.5/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Raw vector

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

CWE Classification

CWE-402CWE-402 CWE-668CWE-668

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

Oct 24, 2026

Identifiers

CVE-2021-31407

GHSA-25xc-jwfq-39jw

References

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

Related vulnerabilities

This CVE is high severity — higher than any of the other 8 CVEs affecting flow-server (highest there: moderate).

CVE-2026-2742CVE-2023-25499CVE-2023-25500GHSA-fr26-qjc8-mvjxGHSA-8vfw-v2jv-9hwcGHSA-c57f-4vp2-jqhmCVE-2020-36321CVE-2018-25007

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 24, 2026

CVE-2021-31407 — flow-server

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-2021-31407 in your dependencies?