How severe is CVE-2021-33604?

CVE-2021-33604 has a CVSS 3.x base score of 2.5, rated low severity. It is exploitable over local access with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2021-33604 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33604?

CVE-2021-33604 primarily affects Vaadin Flow-server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-33604?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-33604 published?

CVE-2021-33604 was published on 2021-06-24 and last updated on 2026-06-17.

CVE-2021-33604

CVE-2021-33604 is a low-severity vulnerability in Vaadin Flow-server with a CVSS 3.x base score of 2.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-172.

Key facts

Severity: Low (CVSS 3.x base score 2.5)
CVSS v2: 1.2
EPSS exploit prediction: 0% (20th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-172
Affected product: Vaadin Flow-server
Published: 2021-06-24
Last modified: 2026-06-17

Description

URL encoding error in development mode handler in com.vaadin:flow-server versions 2.0.0 through 2.6.1 (Vaadin 14.0.0 through 14.6.1), 3.0.0 through 6.0.9 (Vaadin 15.0.0 through 19.0.8) allows local user to execute arbitrary JavaScript code by opening crafted URL in browser.

Frequently asked questions

What is CVE-2021-33604?: URL encoding error in development mode handler in com.vaadin:flow-server versions 2.0.0 through 2.6.1 (Vaadin 14.0.0 through 14.6.1), 3.0.0 through 6.0.9 (Vaadin 15.0.0 through 19.0.8) allows local user to execute arbitrary JavaScript code by opening crafted URL in browser.
How severe is CVE-2021-33604?: CVE-2021-33604 has a CVSS 3.x base score of 2.5, rated low severity. It is exploitable over local access with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2021-33604 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33604?: CVE-2021-33604 primarily affects Vaadin Flow-server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-33604?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-33604 published?: CVE-2021-33604 was published on 2021-06-24 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:vaadin:flow-server:*:*:*:*:*:*:*:*
cpe:2.3:a:vaadin:vaadin:*:*:*:*:*:*:*:*

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