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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

PUBLISHED Reserved 2026-03-10 | Published 2026-05-22 | Updated 2026-05-22 | Assigner Mattermost




MEDIUM: 5.4CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Problem types

CWE-863: Incorrect Authorization

Product status

Default status
unaffected

11.6.0 (semver)
affected

11.5.0 (semver)
affected

11.4.0 (semver)
affected

10.11.0 (semver)
affected

11.7.0
unaffected

11.6.1
unaffected

11.5.4
unaffected

11.4.5
unaffected

10.11.15
unaffected

Credits

eahmed finder

References

mattermost.com/security-updates (MMSA-2026-00628) vendor-advisory

cve.org (CVE-2026-28735)

nvd.nist.gov (CVE-2026-28735)

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