{"cve":"CVE-2026-28735","nvd":{"published":"2026-05-22T17:16:46.260","modified":"2026-07-23T16:10:00.137","status":"Analyzed","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","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N","score":5.4},"cwes":["CWE-863"],"references":["https://mattermost.com/security-updates"],"products":["mattermost:mattermost_server"],"source":"nvd","synced_at":"2026-10-19T22:36:28.938604137+00:00"},"epss":{"cve":"CVE-2026-28735","score":0.00138,"percentile":0.03155,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-r5vf-grcx-5vqp","url":"https://osv.dev/vulnerability/GHSA-r5vf-grcx-5vqp","summary":"Mattermost allows authenticated users to gain access to private repositories","modified":"2026-07-07T16:11:04.161097812Z","packages":[{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","ranges":[">=11.6.0 <11.6.1"],"fixed":["11.6.1"]},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","ranges":[">=11.5.0 <11.5.4"],"fixed":["11.5.4"]},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","ranges":[">=11.4.0 <11.4.5"],"fixed":["11.4.5"]},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","ranges":[">=10.11.0 <10.11.15"],"fixed":["10.11.15"]},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-plugin-github","purl":"pkg:golang/github.com/mattermost/mattermost-plugin-github","ranges":["<1.0.1-0.20260318132218-6e6b740c4852"],"fixed":["1.0.1-0.20260318132218-6e6b740c4852"]}]},{"id":"GO-2026-5839","url":"https://osv.dev/vulnerability/GO-2026-5839","summary":"Mattermost allows authenticated users to gain access to private repositories in github.com/mattermost/mattermost-plugin-github","modified":"2026-07-07T16:01:34.810138159Z","packages":[{"ecosystem":"Go","name":"github.com/mattermost/mattermost-plugin-github","purl":"pkg:golang/github.com/mattermost/mattermost-plugin-github","ranges":["<1.0.1-0.20260318132218-6e6b740c4852"],"fixed":["1.0.1-0.20260318132218-6e6b740c4852"]},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","purl":"pkg:golang/github.com/mattermost/mattermost-server","ranges":[">=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"],"fixed":["10.11.15+incompatible","11.4.5+incompatible","11.5.4+incompatible","11.6.1+incompatible"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}