CVE-2026-28735

mediumpriority · track · 0OT risk · elevatedEPSS 0.001 · 3 %ileDEEUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.14% (3rd) EPSS

CVSS 5.4 · medium

Is it mine?

27 products

Check your exposure

Who says so?

5 sources

cnnvd · enisa_euvd · osv · cert_bund

EPSS · scored 2026-10-27

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL.. Mattermost Advisory ID: MMSA-2026-00628

cvss

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

5.4

010

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

v3.15.4mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:Nsecondary · ENISA EU

v3.15.4mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:Nsecondary · responsibledisclosure@mattermost.comexploitability 2.8 · impact 2.5

v3.15.4mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:Nsecondary · OSV

v3.15mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/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-863USCWE-863US

affected products (27)

Products and version ranges known to be affected.

Mattermost Mattermost <10.11.15all versionscert_bundDE
Mattermost Mattermost <11.4.5all versionscert_bundDE
Mattermost Mattermost <11.5.4all versionscert_bundDE
Mattermost Mattermost <11.6.1all versionscert_bundDE
Mattermost Mattermost <11.7.0all versionscert_bundDE
Mattermost Mattermost< 10.11.15cert_bundDE
Mattermost Mattermost< 11.4.5cert_bundDE
Mattermost Mattermost< 11.5.4cert_bundDE
Mattermost Mattermost< 11.6.1cert_bundDE
Mattermost Mattermost< 11.7.0cert_bundDE
Mattermost Mattermost≤ 10.11.0 ≤10.11.14enisa_euvdEU
Mattermost Mattermost≤ 11.6.0 ≤11.6.0enisa_euvdEU
Mattermost Mattermost≤ 11.5.0 ≤11.5.3enisa_euvdEU
Mattermost Mattermost≤ 11.4.0 ≤11.4.4enisa_euvdEU
mattermost mattermost server10.11.0 → 10.11.15nvdUScpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
mattermost mattermost server11.4.0 → 11.4.5nvdUScpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
mattermost mattermost server11.5.0 → 11.5.4nvdUScpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
mattermost mattermost server11.6.0 → 11.6.1nvdUScpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
Go github.com/mattermost/mattermost-plugin-github< 1.0.1-0.20260318132218-6e6b740c4852osvUSpkg:golang/github.com/mattermost/mattermost-plugin-github
Go github.com/mattermost/mattermost-server10.11.0 → 10.11.15osvUSpkg:golang/github.com/mattermost/mattermost-server

showing 20 of 27

advisories (3)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2026-1173Mattermost: Mehrere Schwachstellen ermöglichen nicht spezifizierten AngriffDeutsch2026-04-19csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Mattermost ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen.
GHSA-r5vf-grcx-5vqpMattermost allows authenticated users to gain access to private repositories2026-05-26ghsa · osvUS
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL. Mattermost Advisory ID: MMSA-2026-00628
GO-2026-5839Mattermost allows authenticated users to gain access to private repositories in github.com/mattermost/mattermost-plugin-github2026-07-07vendor · osvUS
Mattermost allows authenticated users to gain access to private repositories in github.com/mattermost/mattermost-plugin-github

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 2026-05-22modified 2026-07-23

references (3)

External citations — patches, advisories, analysis.

scry

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