How severe is CVE-2025-8402?

CVE-2025-8402 has a CVSS 3.x base score of 4.9, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2025-8402 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-8402?

CVE-2025-8402 primarily affects Mattermost Mattermost Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2025-8402?

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

Does CVE-2025-8402 have an EU (EUVD) identifier?

Yes. CVE-2025-8402 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-25459.

When was CVE-2025-8402 published?

CVE-2025-8402 was published on 2025-08-21 and last updated on 2026-06-17.

CVE-2025-8402

CVE-2025-8402 is a medium-severity vulnerability in Mattermost Mattermost Server with a CVSS 3.x base score of 4.9. 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-476.

Key facts

Severity: Medium (CVSS 3.x base score 4.9)
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-25459
Weakness: CWE-476
Affected product: Mattermost Mattermost Server
Published: 2025-08-21
Last modified: 2026-06-17

Description

Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.10.x <= 10.10.0, 10.9.x <= 10.9.3 fail to validate import data which allows a system admin to crash the server via the bulk import feature.

Frequently asked questions

What is CVE-2025-8402?: Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.10.x <= 10.10.0, 10.9.x <= 10.9.3 fail to validate import data which allows a system admin to crash the server via the bulk import feature.
How severe is CVE-2025-8402?: CVE-2025-8402 has a CVSS 3.x base score of 4.9, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-8402 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-8402?: CVE-2025-8402 primarily affects Mattermost Mattermost Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-8402?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-8402 have an EU (EUVD) identifier?: Yes. CVE-2025-8402 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-25459.
When was CVE-2025-8402 published?: CVE-2025-8402 was published on 2025-08-21 and last updated on 2026-06-17.

References

https://mattermost.com/security-updates

Affected products (2)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:10.10.0:-:*:*:*:*:*:*

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