Malicious remote can invite itself to an arbitrary local channel
Priority MEDIUM 43CWE-284Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · High · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-284.
Summary
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to disallow unsolicited invites to expose access to local channels, when shared channels are enabled, which allows a malicious remote to send an invite with the ID of an existing local channel, and that local channel will then become shared without the consent of the local admin.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00363 30th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 9.10.0, 9.9.1, 9.5.7 +2github.com/mattermost/mattermost/server/v8 (Go): 9.9.1, 9.5.7, 9.7.6 +1
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Mattermost | Mattermost | 9.9.0; 9.5.0 – 9.5.6; 9.7.0 – 9.7.5; 9.8.0 – 9.8.1 | 9.10.0, 9.9.1, 9.5.7, 9.7.6, 9.8.2 | Patch available | CNA |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 9.9.0 to before 9.9.1 | 9.9.1 | Patch available | GHSA-q22q-2rrf-m27p |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 9.5.0 to before 9.5.7 | 9.5.7 | Patch available | GHSA-q22q-2rrf-m27p |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 9.7.0 to before 9.7.6 | 9.7.6 | Patch available | GHSA-q22q-2rrf-m27p |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 9.8.0 to before 9.8.1 | 9.8.1 | Patch available | GHSA-q22q-2rrf-m27p |
- Mattermost VendorMattermost Affected 9.9.0; 9.5.0 – 9.5.6; 9.7.0 – 9.7.5; 9.8.0 – 9.8.1 Fixed in 9.10.0, 9.9.1, 9.5.7, 9.7.6, 9.8.2 Patch available CNA
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 9.9.0 to before 9.9.1 Fixed in 9.9.1 Patch available GHSA-q22q-2rrf-m27p
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 9.5.0 to before 9.5.7 Fixed in 9.5.7 Patch available GHSA-q22q-2rrf-m27p
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 9.7.0 to before 9.7.6 Fixed in 9.7.6 Patch available GHSA-q22q-2rrf-m27p
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 9.8.0 to before 9.8.1 Fixed in 9.8.1 Patch available GHSA-q22q-2rrf-m27p
CPE configurations NVD · 2
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:* | 9.5.0 to before 9.5.7; 9.7.0 to before 9.7.6; 9.8.0 to before 9.8.2 | Vulnerable | Mattermost |
| cpe:2.3:a:mattermost:mattermost:9.9.0:*:*:*:*:*:*:* | 9.9.0 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:* Versions 9.5.0 to before 9.5.7; 9.7.0 to before 9.7.6; 9.8.0 to before 9.8.2 Vulnerable ·Mattermost
- cpe:2.3:a:mattermost:mattermost:9.9.0:*:*:*:*:*:*:* Versions 9.9.0 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 9.10.0, 9.9.1, 9.5.7, 9.7.6, 9.8.2
- Fix · GHSA-q22q-2rrf-m27p github.com/mattermost/mattermost/server/v8 (Go) Fixed in 9.9.1 Advisory →
- Fix · GHSA-q22q-2rrf-m27p github.com/mattermost/mattermost/server/v8 (Go) Fixed in 9.5.7 Advisory →
- Fix · GHSA-q22q-2rrf-m27p github.com/mattermost/mattermost/server/v8 (Go) Fixed in 9.7.6 Advisory →
- Fix · GHSA-q22q-2rrf-m27p github.com/mattermost/mattermost/server/v8 (Go) Fixed in 9.8.1 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2024-39777
- 2026-10-03 Alias added: GHSA-q22q-2rrf-m27p
References
More Mattermost vulnerabilities
- TI-2023-02056 Oauth authorization codes do not expire when deauthorizing an oauth2 app CVSS 3.1CRITICAL 9.1
- TI-2019-15069 An issue was discovered in Mattermost Mobile Apps before 1.26.0. CVSS 3.1CRITICAL 9.1
- TI-2024-26233 Malicious remote can add users to arbitrary teams and channels CVSS 3.1HIGH 8.7
- TI-2024-26746 Permanently local data deletion by malicious remote CVSS 3.1HIGH 8.7
- TI-2023-06508 Injection in Mattermost CVSS 3.1HIGH 8.8
- TI-2024-27253 One-click Client-Side Path Traversal Leading to CSRF in User Management admin page CVSS 3.1HIGH 8.8
Sources
- CVE-2024-39777 · CVE Program
- CVE-2024-39777 · NVD
- FIRST EPSS
- GHSA-q22q-2rrf-m27p · GitHub Advisory Database · CC BY 4.0
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