How severe is CVE-2021-20787?

CVE-2021-20787 has a CVSS 3.x base score of 4.8, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-20787 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20787?

CVE-2021-20787 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-2021-20787?

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

When was CVE-2021-20787 published?

CVE-2021-20787 was published on 2021-07-30 and last updated on 2026-06-17.

CVE-2021-20787

CVE-2021-20787 is a medium-severity vulnerability in Groupsession with a CVSS 3.x base score of 4.8. 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 4.8)
CVSS v2: 3.5
EPSS exploit prediction: 1% (46th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Groupsession
Published: 2021-07-30
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-20787?: 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.
How severe is CVE-2021-20787?: CVE-2021-20787 has a CVSS 3.x base score of 4.8, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-20787 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20787?: CVE-2021-20787 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-2021-20787?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-20787 published?: CVE-2021-20787 was published on 2021-07-30 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:groupsession:groupsession:*:*:*:*:free:*:*:*
cpe:2.3:a:groupsession:groupsession_bycloud:*:*:*:*:*:*:*:*
cpe:2.3:a:groupsession:groupsession_zion:*:*:*:*:*:*:*:*

More vulnerabilities in Groupsession

CVE-2021-20874 — High (CVSS 7.5): Incorrect permission assignment for critical resource vulnerability in GroupSession Free edition ver5.1.1 and earlier,…
CVE-2021-20876 — Medium (CVSS 6.8): Path traversal vulnerability in GroupSession Free edition ver5.1.1 and earlier, GroupSession byCloud ver5.1.1 and…
CVE-2017-2165 — Medium (CVSS 6.5): GroupSession versions 4.6.4 and earlier allows remote authenticated attackers to bypass access restrictions to obtain…
CVE-2025-65120 — Medium (CVSS 6.1): Reflected cross-site scripting vulnerability exists in GroupSession Free edition prior to ver5.7.1, GroupSession…
CVE-2025-57883 — Medium (CVSS 6.1): Reflected cross-site scripting vulnerability exists in GroupSession Free edition prior to ver5.3.0, GroupSession…
CVE-2025-54407 — Medium (CVSS 6.1): Stored cross-site scripting vulnerability exists in GroupSession Free edition prior to ver5.3.0, GroupSession byCloud…

All CVEs affecting Groupsession →

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