CVE-2026-3495
Low
Description
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to escape some variables that could contain malicious content during error page composition which allows an attacker with access to edit some site configuration to execute some malicious code via injecting some JS as part of those values.. Mattermost Advisory ID: MMSA-2026-00622
SeverityLow
CVSS3.8
Exploit probability—
Product
Mattermost Server
PublishedMay 18, 2026
First seenMay 18, 2026
Weakness typeCWE-79Cross-site scripting (XSS)
How to fix
Update
- mattermost mattermost_server10.11.14, 11.5.2 or later
- github.com/mattermost/mattermost/server/v810.11.14, 11.5.2, 8.0.0-20260310115442-5a1ea95044d or later
- github.com/mattermost/mattermost-server5.3.2-0.20260310115442-5a1ea95044dc, 10.11.14+incompatible, 11.5.2+incompatible or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 10.11.0 ≤ v < 10.11.14, 11.5.0 ≤ v < 11.5.2 | 10.11.14, 11.5.2 |
| github.com/mattermost/mattermost/server/v8Go | 10.11.0 ≤ v < 10.11.14, 11.5.0 ≤ v < 11.5.2, v < 8.0.0-20260310115442-5a1ea95044d, No range specified | 10.11.14, 11.5.2, 8.0.0-20260310115442-5a1ea95044d |
| github.com/mattermost/mattermost-serverGo | v < 5.3.2-0.20260310115442-5a1ea95044dc, 10.11.0+incompatible ≤ v < 10.11.14+incompatible, 11.5.0+incompatible ≤ v < 11.5.2+incompatible | 5.3.2-0.20260310115442-5a1ea95044dc, 10.11.14+incompatible, 11.5.2+incompatible |
| github.com/mattermost/mattermost-server/v5Go | No range specified | — |
| github.com/mattermost/mattermost-server/v6Go | No range specified | — |
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