{"id":"CVE-2026-6673","aliases":["GHSA-jqgv-39mg-7c2r"],"title":"Mattermost doesn't authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue share…","summary":"Mattermost doesn't authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret","severity":"medium","cvss":6.4,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H","vendor":"mattermost","product":"github.com/mattermost/mattermost-server","ecosystem":"go","affected":["github.com/mattermost/mattermost-server >= 11.7.0, < 11.7.1","github.com/mattermost/mattermost-server >= 11.6.0, < 11.6.3","github.com/mattermost/mattermost-server >= 11.5.0, < 11.5.6","github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.18"],"patched":["github.com/mattermost/mattermost-server 11.7.1","github.com/mattermost/mattermost-server 11.6.3","github.com/mattermost/mattermost-server 11.5.6","github.com/mattermost/mattermost-server 10.11.18"],"published":"2026-06-22","updated":"2026-09-15","sourceUpdated":"2026-09-15T20:00:39.340161215Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-jqgv-39mg-7c2r","references":[{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-6673"},{"url":"https://github.com/mattermost/mattermost"},{"url":"https://mattermost.com/security-updates"},{"url":"https://github.com/advisories/GHSA-jqgv-39mg-7c2r"}],"tags":["osv","go","ghsa"],"epss":0.00299,"epssPercentile":0.22742,"cwe":["CWE-306"],"ingestedAt":"2026-09-15T20:44:02.611Z","slug":"CVE-2026-6673","body":"## Overview\n\nMattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret and disrupt the Jira integration via POST to /ac/installed during the pending-install window.. Mattermost Advisory ID: MMSA-2026-00654\n\n## Affected packages\n\n- `github.com/mattermost/mattermost-server >= 11.7.0, < 11.7.1`\n- `github.com/mattermost/mattermost-server >= 11.6.0, < 11.6.3`\n- `github.com/mattermost/mattermost-server >= 11.5.0, < 11.5.6`\n- `github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.18`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `github.com/mattermost/mattermost-server 11.7.1`\n- `github.com/mattermost/mattermost-server 11.6.3`\n- `github.com/mattermost/mattermost-server 11.5.6`\n- `github.com/mattermost/mattermost-server 10.11.18`","depth":"sunlit","depthScore":35,"depthScoreParts":{"impact":35.2,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}