How severe is CVE-2017-18871?

CVE-2017-18871 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2017-18871 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (62nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2017-18871?

CVE-2017-18871 primarily affects Mattermost Mattermost Server. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2017-18871?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2017-18871 published?

CVE-2017-18871 was published on 2020-06-19 and last updated on 2026-06-17.

CVE-2017-18871

CVE-2017-18871 is a high-severity vulnerability in Mattermost Mattermost Server with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (62nd percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Mattermost Mattermost Server
Published: 2020-06-19
Last modified: 2026-06-17

Description

An issue was discovered in Mattermost Server before 4.5.0, 4.4.5, 4.3.4, and 4.2.2. It allows attackers to cause a denial of service (application crash) via an @ character before a JavaScript field name.

Frequently asked questions

What is CVE-2017-18871?: An issue was discovered in Mattermost Server before 4.5.0, 4.4.5, 4.3.4, and 4.2.2. It allows attackers to cause a denial of service (application crash) via an @ character before a JavaScript field name.
How severe is CVE-2017-18871?: CVE-2017-18871 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2017-18871 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (62nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2017-18871?: CVE-2017-18871 primarily affects Mattermost Mattermost Server. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2017-18871?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2017-18871 published?: CVE-2017-18871 was published on 2020-06-19 and last updated on 2026-06-17.

References

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

Affected products (5)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:4.5.0:rc1:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:4.5.0:rc2:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:4.5.0:rc3:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:4.5.0:rc4:*:*:*:*:*:*

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