Is CVE-2021-20787 in the CISA KEV catalog?

No. CVE-2021-20787 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-20787?

CVE-2021-20787 has a CVSS v3 base score of 4.8 (MEDIUM).

What is the EPSS score for CVE-2021-20787?

CVE-2021-20787 has an EPSS score of 0.64% (46th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-20787?

Upgrade groupsession to 5.1.0 or later. Fixes are available for 3 affected products.

CVE & CISA-KEV Catalog

CVE-2021-20787

MEDIUM

4.8

CVSS v3

NVD

Description

Cross-site scripting vulnerability in GroupSession (GroupSession Free edition from ver2.2.0 to the version prior to ver5.1.0, GroupSession byCloud from ver3.0.3 to the version prior to ver5.1.0, and GroupSession ZION from ver3.0.3 to the version prior to ver5.1.0) allows a remote attacker to inject an arbitrary script by sending a specially crafted request to a specific URL.

CWE-79Cross-Site Scripting (XSS)

How to fix

Remediation Available

groupsessionNVD

Affected:>= 2.20, < 5.1.0Fixed in:5.1.0CVE-2021-20787derived from NVD

groupsession bycloudNVD

Affected:>= 3.0.3, < 5.1.0Fixed in:5.1.0CVE-2021-20787derived from NVD

groupsession zionNVD

Affected:>= 3.0.3, < 5.1.0Fixed in:5.1.0CVE-2021-20787derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredHigh

User InteractionRequired

ScopeChanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityNone

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

Exploit Intelligence

0.64%probability of exploitation in 30 days

46thpercentile

Moderate risk: more likely to be exploited than 46% of all known CVEs.

References

Vendor Advisory1

groupsession.jp

Third-Party Advisory1

jvn.jp

Related Vulnerabilities

Other CWE-79 (Cross-Site Scripting (XSS)) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2020-11022	Medium	6.9	99%	-	Fix
CVE-2019-3929	Critical	9.8	99%	KEV	Fix
CVE-2020-9496	Medium	6.1	99%	-	-
CVE-2023-28341	Medium	6.1	99%	-	Fix
CVE-2018-12998	Medium	6.1	98%	-	-
CVE-2025-4123	High	7.6	98%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.