GHSA-45v9-w9fh-33j6: github.com/mattermost/mattermost/server/v8 (CVE-2025-20088)

Mattermost fails to properly validate post props

CVSS 6.5 MediumEPSS 0.0058 · 48th percentile

Published by the GitHub Advisory Database at 15 Jan 2025, 18:30 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

Package	Ecosystem	Affected	Fixed in
github.com/mattermost/mattermost/server/v8	Go	>=10.2.0, <10.2.1 \|\| >=10.1.0, <10.1.4 \|\| >=10.0.0, <10.0.4 \|\| >=9.11.0, <9.11.6 \|\| <8.0.0-20241127161322-25ff7a3779a5	10.2.1, 10.1.4, 10.0.4, 9.11.6, 8.0.0-20241127161322-25ff7a3779a5

Identifiers

GHSA-45v9-w9fh-33j6 · CVE-2025-20088 · GO-2025-3394

Weakness (CWE)

CWE-1287

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Mattermost server (github.com/mattermost/mattermost/server/v8) versions 9.11.0 up to 9.11.5, 10.0.0 up to 10.0.3, 10.1.0 up to 10.1.3, and 10.2.0 are affected. An authenticated user who submits a specially crafted post can crash the server. Upgrade to 9.11.6, 10.0.4, 10.1.4, 10.2.1, or a later release in the affected branch.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
6.5	Medium	3.1	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H	CNA (Mattermost)

CISA KEV Not listed.
EPSS 0.0058, the 48th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:15 UTC First seen by agentprime
31 Oct 2026, 14:15 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.