CVE-2026-28735
Low
No strong exploitation signal.
CVSS base
5.4
MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
EPSS — probability of exploitation (30 days)
0.1%
3.5th percentile
CISA KEV
Not listed
Weakness / dates
CWE-863
Published 2026-05-22 · modified 2026-07-23
CVSS breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
| Attack Vector | N | Network |
| Attack Complexity | L | Low |
| Privileges Required | L | Low |
| User Interaction | N | None |
| Scope | U | Unchanged |
| Confidentiality | L | Low |
| Integrity | L | Low |
| Availability | N | None |
Timeline
- 2026-05-22 — Published (NVD)
- 2026-07-23 — Last modified (NVD)
Description
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