CVE-2021-20787

Name: CVE-2021-20787
Creator: NVD / NIST
Published: 2021-07-30T14:15:14.84+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.8/10EPSS 0.64%

Last modified Jun 17, 2026

CVE-2021-20787 is a medium-severity vulnerability rated 4.8/10 on the CVSS scale. 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.. EPSS estimates a 0.64% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

4.8/10

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

EPSS Probability

0.64%

46.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Groupsession	Groupsession	>= 2.20, < 5.1.0
Groupsession	Groupsession Bycloud	>= 3.0.3, < 5.1.0
Groupsession	Groupsession Zion	>= 3.0.3, < 5.1.0

References

https://groupsession.jp/info/info-news/security202107Vendor Advisory
https://jvn.jp/en/jp/JVN86026700/index.htmlThird Party Advisory
https://groupsession.jp/info/info-news/security202107Vendor Advisory
https://jvn.jp/en/jp/JVN86026700/index.htmlThird Party Advisory

Timeline

Published: Jul 30, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-20787?

How severe is CVE-2021-20787?

CVE-2021-20787 has a CVSS score of 4.8/10 (MEDIUM severity). The EPSS model estimates a 0.64% probability of exploitation in the next 30 days.

How do I fix CVE-2021-20787?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-20787?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST