---
id: "CVE-2026-93848"
kind: "vulnerability"
aliases: ["CVE-2026-93848"]
title: "Mattermost: OpenID discovery skips internal-address filtering, leaking reachability"
severity: "low"
cvss: 2.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["mattermost", "package", "self-hosted"]
not_affected_if: ["default-config", "managed-hosting"]
published_at: "2026-10-26T15:16:46+00:00"
first_seen_at: "2026-10-26T16:02:26+00:00"
updated_at: "2026-10-26T16:03:58+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93848", "first_seen_at": "2026-10-26T16:02:26+00:00"}]
---

# Mattermost: OpenID discovery skips internal-address filtering, leaking reachability

Mattermost 11.7.x up to 11.7.10 does not apply its outbound internal-connection filter to the OpenID discovery request. A system administrator can use unauthenticated login attempts to learn which internal addresses and ports the server can reach.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the running Mattermost server version with `mattermost version` or the System Console version page; affected range is `11.7.0` through `11.7.10`.
- Confirm whether OpenID/GitLab-style login is configured in the System Console under Authentication.

## Fix

- Upgrade Mattermost to a version newer than `11.7.10` (exact fixed version: unknown, see MMSA-2026-00774).

## Timeline

- 2026-10-26T16:02:26+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-93848

## From the sources

Mattermost versions 11.7.x <= 11.7.10 fail to apply outbound internal-connection filtering to the OpenID discovery endpoint request which allows a System Administrator to determine whether internal addresses and ports are reachable from the server via an unauthenticated login request that triggers the discovery fetch.. Mattermost Advisory ID: MMSA-2026-00774

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_