CVE-2025-21088

WebApp crash via improper validation of proto style in attachments

Description

Mattermost versions 10.2.x <= 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly validate the style of proto supplied to an action's style in post.props.attachments, which allows an attacker to crash the frontend via crafted malicious input.

Remediation

Solution:

  • Update Mattermost to versions 10.3.0, 2.23.0, 10.2.1, 9.11.6, 10.0.4, 10.1.4 or higher.

Category

6.5
CVSS
Severity: Medium
CVSS 3.1 •
EPSS 0.08%
Affected: Mattermost Mattermost
Published at:
Updated at:

References

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

Frequently Asked Questions

What is the severity of CVE-2025-21088?
CVE-2025-21088 has been scored as a medium severity vulnerability.
How to fix CVE-2025-21088?
To fix CVE-2025-21088: Update Mattermost to versions 10.3.0, 2.23.0, 10.2.1, 9.11.6, 10.0.4, 10.1.4 or higher.
Is CVE-2025-21088 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2025-21088 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2025-21088?
CVE-2025-21088 affects Mattermost Mattermost.
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