🛡️ CVE-2026-28735 — mattermost-server

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality low, integrity low, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

• Attack vector: Network — reachable from anywhere that can route to the service.
• Attack complexity: Low — the attack works reliably, with no preparation.
• Privileges required: Low — an ordinary user account is enough.
• User interaction: None — nobody has to be tricked into anything.
• Scope: Unchanged — the damage stays inside the vulnerable component.
• Confidentiality impact: Low — limited, and the attacker does not choose what is affected.
• Integrity impact: Low — limited, and the attacker does not choose what is affected.
• Availability impact: None.

Weakness class

CVE-2026-28735 is classified as CWE-863: Incorrect Authorization. An authorisation check runs but reaches the wrong conclusion, permitting actions it should refuse.

Affected software

CVE-2026-28735 is recorded against 3 packages.

• github.com/mattermost/mattermost-plugin-github
• github.com/mattermost/mattermost-server
• mattermost-server (from 11.6.0 up to 11.6.1)

Timeline and source

Published on 7 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com (Advisory)
nvd.nist.gov (Advisory)
github.com (Fix)
mattermost.com (Web)

Other advisories for this package

github.com/mattermost/mattermost-plugin-github has other advisories on record. If you are patching this one, these are worth checking on the same host:

• CVE-2026-5308 (8.0 High, published 7 Jul 2026)
• CVE-2026-4646 (published 7 Jul 2026)
• CVE-2025-13352 (2.0 Low, published 17 Dec 2025)

Same weakness in other software

These advisories are the same class of weakness (CWE-863: Incorrect Authorization) in other software:

• CVE-2025-14562 (2.0 Low, published 17 Aug 2026)
• CVE-2025-30238 (published 10 Aug 2026)
• CVE-2025-15674 (2.7 Low, published 6 Aug 2026)
• CVE-2025-10656 (9.8 Critical, published 29 Jul 2026)
• CVE-2023-27523 (5.0 Medium, published 7 Jul 2026)
• CVE-2024-39025 (8.0 High, published 7 Jul 2026)
• CVE-2024-24779 (5.0 Medium, published 7 Jul 2026)
• CVE-2024-26016 (5.0 Medium, published 7 Jul 2026)

Details

Affected Packages

References