How severe is CVE-2018-21252?

CVE-2018-21252 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2018-21252 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (45th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-21252?

CVE-2018-21252 primarily affects Mattermost Mattermost Server. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2018-21252?

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

When was CVE-2018-21252 published?

CVE-2018-21252 was published on 2020-06-19 and last updated on 2026-06-17.

CVE-2018-21252

CVE-2018-21252 is a medium-severity vulnerability in Mattermost Mattermost Server with a CVSS 3.x base score of 4.3. 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-732.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
CVSS v2: 4.0
EPSS exploit prediction: 1% (45th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-732
Affected product: Mattermost Mattermost Server
Published: 2020-06-19
Last modified: 2026-06-17

Description

An issue was discovered in Mattermost Server before 5.2, 5.1.1, 5.0.3, and 4.10.3. Attackers could use multiple e-mail addresses to bypass a domain-based policy for signups.

Frequently asked questions

What is CVE-2018-21252?: An issue was discovered in Mattermost Server before 5.2, 5.1.1, 5.0.3, and 4.10.3. Attackers could use multiple e-mail addresses to bypass a domain-based policy for signups.
How severe is CVE-2018-21252?: CVE-2018-21252 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2018-21252 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (45th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-21252?: CVE-2018-21252 primarily affects Mattermost Mattermost Server. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2018-21252?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2018-21252 published?: CVE-2018-21252 was published on 2020-06-19 and last updated on 2026-06-17.

References

https://mattermost.com/security-updates/

Affected products (7)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:5.2.0:rc1:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:5.2.0:rc2:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:5.2.0:rc3:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:5.2.0:rc4:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:5.2.0:rc5:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:5.2.0:rc6:*:*:*:*:*:*

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