How severe is CVE-2025-66284?

CVE-2025-66284 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2025-66284 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (4th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-66284?

CVE-2025-66284 primarily affects Groupsession. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2025-66284?

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

Does CVE-2025-66284 have an EU (EUVD) identifier?

Yes. CVE-2025-66284 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-203025.

When was CVE-2025-66284 published?

CVE-2025-66284 was published on 2025-12-12 and last updated on 2026-06-17.

CVE-2025-66284

CVE-2025-66284 is a medium-severity vulnerability in Groupsession with a CVSS 3.x base score of 5.4. 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-79.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
CVSS v4: 4.8
EPSS exploit prediction: 0% (4th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-203025
Weakness: CWE-79
Affected product: Groupsession
Published: 2025-12-12
Last modified: 2026-06-17

Description

Stored cross-site scripting vulnerabilities exist in GroupSession Free edition prior to ver5.7.1, GroupSession byCloud prior to ver5.7.1, and GroupSession ZION prior to ver5.7.1. A logged-in user can prepare a malicious page or URL, and an arbitrary script may be executed on the web browser when another user accesses it.

Frequently asked questions

What is CVE-2025-66284?: Stored cross-site scripting vulnerabilities exist in GroupSession Free edition prior to ver5.7.1, GroupSession byCloud prior to ver5.7.1, and GroupSession ZION prior to ver5.7.1. A logged-in user can prepare a malicious page or URL, and an arbitrary script may be executed on the web browser when another user accesses it.
How severe is CVE-2025-66284?: CVE-2025-66284 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2025-66284 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (4th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-66284?: CVE-2025-66284 primarily affects Groupsession. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-66284?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-66284 have an EU (EUVD) identifier?: Yes. CVE-2025-66284 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-203025.
When was CVE-2025-66284 published?: CVE-2025-66284 was published on 2025-12-12 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:groupsession:groupsession:*:*:*:*:bycloud:*:*:*
cpe:2.3:a:groupsession:groupsession:*:*:*:*:free:*:*:*
cpe:2.3:a:groupsession:groupsession:*:*:*:*:zion:*:*:*

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CVE-2021-20874 — High (CVSS 7.5): Incorrect permission assignment for critical resource vulnerability in GroupSession Free edition ver5.1.1 and earlier,…
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