CVE-2026-8823 json
User Manager can demote bot accounts to guest without bot-management permission
published 2026-06-22 4 mo ago modified 2026-10-01 38 d ago also GHSA-xmfh-3ccg-c9fx , GO-2026-6547 , EUVD-2026-38276
- cvss
- 3.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 24%
- public exploits
- 0
- none known
Summary
Mattermost versions 11.7.x <= 11.7.0, 10.11.x <= 10.11.17 fail to validate bot targets when demoting users to guests which allows a lower-privileged administrator to degrade arbitrary bot accounts via the standard demote-user API.. Mattermost Advisory ID: MMSA-2026-00669
Patch / fix
- go github.com/mattermost/mattermost-server 10.11.18, 10.11.18+incompatible, 11.7.1, 11.7.1+incompatible
- go github.com/mattermost/mattermost/server/v8 8.0.0-20260518160100-9bd77d3fc4d2
- Mattermost Mattermost 10.11.18, 11.7.1, 11.8.0
- github.com/mattermost/mattermost@7972fc5 commit
- github.com/mattermost/mattermost@9bd77d3 commit
- github.com/mattermost/mattermost@c9bf360 commit
- github.com/mattermost/mattermost@d9a55e3 commit
- github.com/mattermost/mattermost#36487 pull request
- github.com/mattermost/mattermost/releases/tag/v10.11.18 release
- github.com/mattermost/mattermost/releases/tag/v11.7.1 release
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 4 mo ago
Exploit prediction
0.32% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 3.8 | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L |
| GitHub | 3.1 | 3.8 | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/mattermost/mattermost-server | >=11.7.0, <11.7.1 >=10.11.0, <10.11.18 >=10.11.0+incompatible, <10.11.18+incompatible >=11.7.0+incompatible, <11.7.1+incompatible |
11.7.1 10.11.18 10.11.18+incompatible 11.7.1+incompatible |
| go | github.com/mattermost/mattermost/server/v8 | <8.0.0-20260518160100-9bd77d3fc4d2 |
8.0.0-20260518160100-9bd77d3fc4d2 |
| go | github.com/mattermost/mattermost-server/v5 | all versions |
no fix listed |
| go | github.com/mattermost/mattermost-server/v6 | all versions |
no fix listed |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-863 Incorrect Authorization
References
-
github.com
/mattermost/mattermost/pull/36487
web
-
github.com
/mattermost/mattermost/commit/7972fc53f5c0b0175879a9737308a87b42db1f0b
web
-
github.com
/mattermost/mattermost/commit/9bd77d3fc4d2af3f7f0259a205174e76a1a276e1
web
-
github.com
/mattermost/mattermost/commit/c9bf3609fb9a3e5c2de94c50742c9b91fd723e3d
web
-
github.com
/mattermost/mattermost/commit/d9a55e394cd5bc15edb49e9606bec8fec03ac4c6
web
-
mattermost.com
/security-updates
vendor-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-8823
advisory
-
docs.mattermost.com
/security-guide/security-updates
web
-
github.com
/mattermost/mattermost
package
-
github.com
/mattermost/mattermost/releases/tag/v10.11.18
web
-
github.com
/mattermost/mattermost/releases/tag/v11.7.1
web
-
github.com
/advisories/GHSA-xmfh-3ccg-c9fx
advisory
Sources
- CVE List CVE-2026-8823
- GitHub Advisory GHSA-xmfh-3ccg-c9fx
- NVD CVE-2026-8823
- OSV GO-2026-6547
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.