CVE-2026-6673Mattermost Jira plugin had unauthenticated {{/ac/installed}} lifecycle callback during pending Jira Cloud install
- 6.4MediumCVSS base score
- 0.30%Exploitation in 30 daysEPSS · top 77% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
Mattermost 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
Timeline
ID reserved
By Mattermost
- 2 months later
· 2 months later
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| MattermostCNA (assigner) | 3.1 | Medium6.4 | CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H |
| NVDNVD · Analyzed | 3.1 | Medium6.4 | CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.30% · top 77% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.4.
Affected products
- affected 11.7.0 – ≤ 11.7.0
- affected 11.6.0 – ≤ 11.6.2
- affected 11.5.0 – ≤ 11.5.5
- affected 10.11.0 – ≤ 10.11.17
- unaffected 11.8.0
- unaffected 11.7.1
- unaffected 11.6.3
- unaffected 11.5.6
- unaffected 10.11.18
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Gogithub.com/mattermost/mattermost-serverGHSA-jqgv-39mg-7c2r (opens in a new tab)
What to do
Solution: Update Mattermost to versions 11.8.0, 11.7.1, 11.6.3, 11.5.6, 10.11.18 or higher.
References
References1
- MMSA-2026-00654 (opens in a new tab)vendor-advisory
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-38249 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-jqgv-39mg-7c2r (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-6673)Record last updated .