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CVE-2021-20789

21
FAUCET Score

CVE-2021-20789 is an open redirect vulnerability affecting GroupSession Free (v2.2.0 to <5.1.0), GroupSession byCloud (v3.0.3 to <5.1.0), and GroupSession ZION (v3.0.3 to <5.1.0). This flaw allows an unauthenticated attacker to redirect users to arbitrary malicious websites through a specially crafted URL, facilitating phishing attacks. The vulnerability has a CVSSv3.1 score of 6.1 (Medium), indicating a network-based attack with low complexity, requiring user interaction, and resulting in low impact to confidentiality and integrity. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage regarding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
>= 2.20, < 5.1.0CPE matchmatch criteria
cpe:2.3:a:groupsession:groupsession:*:*:*:*:free:*:*:*
>= 3.0.3, < 5.1.0CPE matchmatch criteria
cpe:2.3:a:groupsession:groupsession_bycloud:*:*:*:*:*:*:*:*
>= 3.0.3, < 5.1.0CPE matchmatch criteria
cpe:2.3:a:groupsession:groupsession_zion:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.1MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
2.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.87%
Probability of exploitation in next 30 days
EPSS Percentile
55.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0087 is in the 66th percentile among its peer group of 26,236 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

groupsession.jp / info/info-news/security202107
Vendor Advisory
jvn.jp / en/jp/JVN86026700/index.html
Third Party Advisory