CVE-2026-6673

mediumpriority · track · 0OT risk · elevatedEPSS 0.003 · 23 %ileDEEUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.30% (23rd) EPSS

CVSS 6.4 · medium

Is it mine?

30 products

Check your exposure

Who says so?

5 sources

cnnvd · enisa_euvd · osv · cert_bund

EPSS · scored 2026-10-28

Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret and disrupt the Jira integration via POST to /ac/installed during the pending-install window.. Mattermost Advisory ID: MMSA-2026-00654

cvss

Technical severity, 0–10. One row per scoring source.

6.4

010

base score 0–10 · higher = more severe · hover a vector to decode

v3.16.4mediumCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:Hsecondary · ENISA EU

v3.16.4mediumCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:Hsecondary · responsibledisclosure@mattermost.comexploitability 1.2 · impact 5.2

v3.16.4mediumCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:Hsecondary · OSV

v3.15.9mediumCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Trackcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-306USCWE-306US

affected products (30)

Products and version ranges known to be affected.

Mattermost Mattermost Desktop <5.13.6all versionscert_bundDE
Mattermost Mattermost Desktop <6.2all versionscert_bundDE
Mattermost Mattermost Server <10.11.18all versionscert_bundDE
Mattermost Mattermost Server <11.5.6all versionscert_bundDE
Mattermost Mattermost Server <11.6.3all versionscert_bundDE
Mattermost Mattermost Server <11.7.1all versionscert_bundDE
Mattermost Mattermost Server <11.8.0all versionscert_bundDE
Mattermost Mattermost≤ Desktop <5.13.6cert_bundDE
Mattermost Mattermost≤ Desktop <6.2cert_bundDE
Mattermost Mattermost≤ Server <10.11.18cert_bundDE
Mattermost Mattermost≤ Server <11.5.6cert_bundDE
Mattermost Mattermost≤ Server <11.6.3cert_bundDE
Mattermost Mattermost≤ Server <11.7.1cert_bundDE
Mattermost Mattermost≤ Server <11.8.0cert_bundDE
Mattermost Mattermost≤ 11.5.0 ≤11.5.5enisa_euvdEU
Mattermost Mattermost≤ 11.6.0 ≤11.6.2enisa_euvdEU
Mattermost Mattermost≤ 10.11.0 ≤10.11.17enisa_euvdEU
Mattermost Mattermost≤ 11.7.0 ≤11.7.0enisa_euvdEU
mattermost mattermost server10.11.0 → 10.11.18nvdUScpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
mattermost mattermost server11.5.0 → 11.5.6nvdUScpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

showing 20 of 30

advisories (3)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2026-1650Mattermost (Desktop, Server und Mobile): Mehrere SchwachstellenDeutsch2026-05-21csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Mattermost ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen und um Informationen offenzulegen.
GHSA-jqgv-39mg-7c2rMattermost doesn't authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret2026-06-22ghsa · osvUS
Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret and disrupt the Jira integration via POST to /ac/installed during the pending-install window.. Mattermost Advisory ID: MMSA-2026-00654
GO-2026-6483Mattermost doesn't authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret in github.com/mattermost/mattermost-server2026-09-28vendor · osvUS
Mattermost doesn't authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret in github.com/mattermost/mattermost-server

also known as (5)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd osv cert_bund nvd NVD CVE.org MITRE

published 2026-06-22modified 2026-06-23

references (3)

External citations — patches, advisories, analysis.

scry

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