CVE-2026-28735 json
GitHub OAuth Scope Validation
published 2026-05-22 5 mo ago modified 2026-07-23 3 mo ago also GHSA-r5vf-grcx-5vqp , GO-2026-5839 , EUVD-2026-31465
- cvss
- 5.4
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.1%
- EPSS 0.1% chance of exploitation in 30 days, percentile 3%
- public exploits
- 0
- none known
Summary
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
Patch / fix
- go github.com/mattermost/mattermost-server 10.11.15, 10.11.15+incompatible, 11.4.5, 11.4.5+incompatible, 11.5.4, 11.5.4+incompatible, 11.6.1, 11.6.1+incompatible
- go github.com/mattermost/mattermost-plugin-github 1.0.1-0.20260318132218-6e6b740c4852
- Mattermost Mattermost 10.11.15, 11.4.5, 11.5.4, 11.6.1, 11.7.0
- govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
opensuse advisories openSUSE-SU-2026:21483-1
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 5 mo ago
Exploit prediction
0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.4 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N |
| GitHub | 3.1 | 5.4 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/mattermost/mattermost-server | >=11.6.0, <11.6.1 >=11.5.0, <11.5.4 >=11.4.0, <11.4.5 >=10.11.0, <10.11.15 >=10.11.0+incompatible, <10.11.15+incompatible >=11.4.0+incompatible, <11.4.5+incompatible >=11.5.0+incompatible, <11.5.4+incompatible >=11.6.0+incompatible, <11.6.1+incompatible |
11.6.1 11.5.4 11.4.5 10.11.15 10.11.15+incompatible 11.4.5+incompatible 11.5.4+incompatible 11.6.1+incompatible |
| go | github.com/mattermost/mattermost-plugin-github | <1.0.1-0.20260318132218-6e6b740c4852 |
1.0.1-0.20260318132218-6e6b740c4852 |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-863 Incorrect Authorization
References
-
github.com
/mattermost/mattermost-plugin-github/commit/6e6b740c4852cdfa136ee0ced160da832285c353
web, patch
-
mattermost.com
/security-updates
vendor-advisory, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-28735
advisory
-
github.com
/mattermost/mattermost
package
-
github.com
/advisories/GHSA-r5vf-grcx-5vqp
advisory
Sources
- CVE List CVE-2026-28735
- GitHub Advisory GHSA-r5vf-grcx-5vqp
- NVD CVE-2026-28735
- OSV GO-2026-5839
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.