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CVE Vulnerability Details :
CVE-2026-28735
PUBLISHED
More InfoOfficial Page
Assigner-Mattermost
Assigner Org ID-9302f53e-dde5-4bf3-b2f2-a83f91ac0eee
View Known Exploited Vulnerability (KEV) details
Published At-22 May, 2026 | 16:26
Updated At-22 May, 2026 | 16:56
Rejected At-
▼CVE Numbering Authority (CNA)
GitHub OAuth Scope Validation

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

Affected Products
Vendor
Mattermost, Inc.Mattermost
Product
Mattermost
Default Status
unaffected
Versions
Affected
  • From 11.6.0 through 11.6.0 (semver)
  • From 11.5.0 through 11.5.3 (semver)
  • From 11.4.0 through 11.4.4 (semver)
  • From 10.11.0 through 10.11.14 (semver)
Unaffected
  • 11.7.0
  • 11.6.1
  • 11.5.4
  • 11.4.5
  • 10.11.15
Problem Types
TypeCWE IDDescription
CWECWE-863CWE-863: Incorrect Authorization
Type: CWE
CWE ID: CWE-863
Description: CWE-863: Incorrect Authorization
Metrics
VersionBase scoreBase severityVector
3.15.4MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Version: 3.1
Base score: 5.4
Base severity: MEDIUM
Vector:
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher.

Configurations
Workarounds
Exploits
Credits
finder
eahmed
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
https://mattermost.com/security-updates
vendor-advisory
Hyperlink: https://mattermost.com/security-updates
Resource:
vendor-advisory
▼Authorized Data Publishers (ADP)
CISA ADP Vulnrichment
Affected Products
Metrics
VersionBase scoreBase severityVector
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
Details not found