CVE-2026-93848
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Outbound Internal-Connection Filtering Bypass in Mattermost

Publication date: 2026-10-26

Last updated on: 2026-10-26

Assigner: Mattermost, Inc.

Description
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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Meta Information

Published
2026-10-26
Last Modified
2026-10-26
Generated
2026-10-26
AI Q&A
2026-10-26
EPSS Evaluated
N/A
NVD
CVE-2026-93848
EUVD
EUVD-2026-109939

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
Mattermost Mattermost 11.7.0

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-918 The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

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Executive Summary

Mattermost versions between 11.7.0 and 11.7.10 have a flaw where outbound internal-connection filtering is not applied to the OpenID discovery endpoint request. This allows a System Administrator to check if internal addresses and ports are reachable from the server by triggering an unauthenticated login request that initiates the discovery fetch.

Impact Analysis

An attacker with System Administrator access could exploit this to map internal network infrastructure, identifying reachable internal addresses and ports. This could aid in further attacks targeting internal systems.

Mitigation Strategies

Upgrade Mattermost to a version higher than 11.7.10 where the outbound internal-connection filtering issue has been fixed.

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