Mattermost versions 10.11.x <= 10.11.18, 11.6.x <= 11.6.3, 11.5.x <= 11.5.6 fail to validate attachment URLs against internal or private IP ranges in the Mattermost Agents plugin MCP server which allows an attacker with access to the MCP server in stdio mode to perform server-side request forgery (SSRF) and exfiltrate data from internal network services via supplying internal URLs as file attachments in post creation requests.. Mattermost Advisory ID: MMSA-2026-00635
| Vendor | Product | Version(s) | CPE |
|---|---|---|---|
>= 10.11.0, < 10.11.19CPE matchmatch criteria | cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | ||
>= 11.5.0, < 11.5.7CPE matchmatch criteria | cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | ||
>= 11.6.0, < 11.6.4CPE matchmatch criteria | cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | ||
>= 10.11.0, <= 10.11.18CPE match | cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:* | ||
>= 11.5.0, <= 11.5.6CPE match | cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:* |
CVSS version used by this source: 3.1
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.
No media coverage found for this CVE.
The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.
Remediation records are not available for this CVE.