Skip to content
EXYS
Back to the CVEs

CVE-2026-12985

9.3, critical

Mattermost Open Redirect Vulnerability

NVD (opens in a new tab) CVE.org (opens in a new tab)
CVSS
9.3, critical critical CVSS v3.1
EPSS, next 30 days
0.3% higher than 17.6% of scored CVEs
Exploitation
No public evidence
Published
14 Sept 2026a month ago

Description

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7 Mattermost failed to validate Dynamic Client Registration redirect URIs by URL component (matching glob patterns against the raw URI string instead) which allows a remote unauthenticated attacker to register an OAuth client with an attacker-controlled callback host that bypasses the configured redirect URI allowlist via a crafted redirect URI that places an allowlisted host/path suffix inside the query string.. Mattermost Advisory ID: MMSA-2026-00700

Details

Vendor
Mattermost
Product
Mattermost
Weakness
CWE-601 (opens in a new tab)
Status
Analyzed
Updated
7 Oct 2026
Assigner
responsibledisclosure@mattermost.com

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

References 1

Advisories 1

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Beyond this page

Is CVE-2026-12985 in your network?

This page tells you how dangerous CVE-2026-12985 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

  • EXYS7600 OCELOT

    Find it before attackers do

    Ocelot scans your network on a schedule and reports every vulnerability it finds by its CVE identifier, with its CVSS score and how many of your hosts are affected. A finding like CVE-2026-12985 comes with the devices to patch.

    Learn more about EXYS7600 OCELOT

  • EXYS7950 KONDRA

    Detect it if it's exploited

    Until the patch is applied, Kondra monitors your network, events and endpoints in real time. It keeps an inventory of the software installed on every endpoint, and its anomaly detection rules flag what an attacker does once inside.

    Learn more about EXYS7950 KONDRA
Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 17 Oct 2026, not the live upstream state.