CVE-2026-21386

mediumpriority · track · 0EPSS 0.002 · 8 %ileDEEURUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.19% (8th) EPSS

CVSS 4.3 · medium

Is it mine?

36 products

Check your exposure

Who says so?

5 sources

cnnvd · enisa_euvd · fstec_bdu · osv

EPSS · scored 2026-10-27

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to use consistent error responses when handling the /mute command which allows an authenticated team member to enumerate private channels they are not authorized to know about via differing error messages for nonexistent versus private channels. Mattermost Advisory ID: MMSA-2026-00588

cvss

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

4.3

010

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

v3.14.3mediumAV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:Nsecondary · FSTEC (BDU) RU

v3.14.3mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:Nsecondary · ENISA EU

v3.14.3mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:Nsecondary · responsibledisclosure@mattermost.comexploitability 2.8 · impact 1.4

v3.14.3mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:Nsecondary · OSV

v3.14mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N/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-200USCWE-203USCWE-203US

affected products (36)

Products and version ranges known to be affected.

Mattermost Mattermost Desktop <5.13.3.0all versionscert_bundDE
Mattermost Mattermost Desktop <5.13.4.0all versionscert_bundDE
Mattermost Mattermost Plugins <10.11.11all versionscert_bundDE
Mattermost Mattermost Plugins <2.3.1.0all versionscert_bundDE
Mattermost Mattermost Server <10.11.11all versionscert_bundDE
Mattermost Mattermost Server <11.2.3all versionscert_bundDE
Mattermost Mattermost Server <11.3.1all versionscert_bundDE
Mattermost Mattermost Server <11.4.0all versionscert_bundDE
Mattermost Mattermost≤ Plugins <2.3.1.0cert_bundDE
Mattermost Mattermost≤ Desktop <5.13.3.0cert_bundDE
Mattermost Mattermost≤ Desktop <5.13.4.0cert_bundDE
Mattermost Mattermost≤ Plugins <10.11.11cert_bundDE
Mattermost Mattermost≤ Server <10.11.11cert_bundDE
Mattermost Mattermost≤ Server <11.2.3cert_bundDE
Mattermost Mattermost≤ Server <11.3.1cert_bundDE
Mattermost Mattermost≤ Server <11.4.0cert_bundDE
Mattermost Mattermost≤ 10.11.0 ≤10.11.10enisa_euvdEU
Mattermost Mattermost≤ 11.2.0 ≤11.2.2enisa_euvdEU
Mattermost Mattermost≤ 11.3.0 ≤11.3.0enisa_euvdEU
Mattermost Inc Mattermost≤ 11.2.3fstec_bduRU

showing 20 of 36

advisories (3)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2026-0422Mattermost: Mehrere SchwachstellenDeutsch2026-02-15csaf · cert_bundDE
Ein authentisierter Angreifer kann mehrere Schwachstellen in Mattermost ausnutzen, um falsche Informationen anzuzeigen, Informationen offenzulegen, Sicherheitskontrollen zu umgehen und eine Denial-of-Service-Situation zu erzeugen.
GHSA-5mr9-crcg-8wh2Mattermost fails to use consistent error responses when handling the /mute command2026-03-16ghsa · osvUS
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to use consistent error responses when handling the /mute command which allows an authenticated team member to enumerate private channels they are not authorized to know about via differing error messages for nonexistent versus private channels. Mattermost Advisory ID: MMSA-2026-00588
GO-2026-4744Mattermost fails to use consistent error responses when handling the /mute command in github.com/mattermost/mattermost-server2026-03-23vendor · osvUS
Mattermost fails to use consistent error responses when handling the /mute command in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. (If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.) The additional affected modules and versions are: github.com/mattermost/mattermost-server/v5 before v5.3.2-0.20260130144323-5bb5261c72fa.

also known as (6)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu osv cert_bund NVD CVE.org MITRE

published 2026-03-16modified 2026-06-17

references (3)

External citations — patches, advisories, analysis.

scry

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