OAuth authorization code client binding not enforced during token redemption in Mattermost
Priority LOW 17CWE-305Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- High
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub.
Summary
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to enforce client identity binding during the OAuth authorization code redemption flow which allows an authenticated OAuth client to redeem authorization codes issued to a different client via a crafted token exchange request.. Mattermost Advisory ID: MMSA-2026-00570
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00118 1st percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.6.0, 11.5.2, 10.11.14github.com/mattermost/mattermost/server/v8 (Go): 11.5.2, 10.11.14, 8.0.0-20260318173148-e9ae890a013b+1 more product
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
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 | 11.5.0 – 11.5.1; 10.11.0 – 10.11.13 | 11.6.0, 11.5.2, 10.11.14 | Patch available | CNA |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 11.5.0 to before 11.5.2 | 11.5.2 | Patch available | GHSA-jp3f-x449-4q75 |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 10.11.0 to before 10.11.14 | 10.11.14 | Patch available | GHSA-jp3f-x449-4q75 |
| — | github.com/mattermost/mattermost/server/v8 (Go) | before 8.0.0-20260318173148-e9ae890a013b | 8.0.0-20260318173148-e9ae890a013b | Patch available | GHSA-jp3f-x449-4q75 |
| — | github.com/mattermost/mattermost-server (Go) | before 5.3.2-0.20260318173148-e9ae890a013b | 5.3.2-0.20260318173148-e9ae890a013b | Patch available | GHSA-jp3f-x449-4q75 |
- Mattermost VendorMattermost Affected 11.5.0 – 11.5.1; 10.11.0 – 10.11.13 Fixed in 11.6.0, 11.5.2, 10.11.14 Patch available CNA
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 11.5.0 to before 11.5.2 Fixed in 11.5.2 Patch available GHSA-jp3f-x449-4q75
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 10.11.0 to before 10.11.14 Fixed in 10.11.14 Patch available GHSA-jp3f-x449-4q75
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected before 8.0.0-20260318173148-e9ae890a013b Fixed in 8.0.0-20260318173148-e9ae890a013b Patch available GHSA-jp3f-x449-4q75
- github.com/mattermost/mattermost-server (Go) Vendor— Affected before 5.3.2-0.20260318173148-e9ae890a013b Fixed in 5.3.2-0.20260318173148-e9ae890a013b Patch available GHSA-jp3f-x449-4q75
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | 10.11.0 to before 10.11.14; 11.5.0 to before 11.5.2 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.14; 11.5.0 to before 11.5.2 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 11.6.0, 11.5.2, 10.11.14
- Fix · GHSA-jp3f-x449-4q75 github.com/mattermost/mattermost/server/v8 (Go) Fixed in 11.5.2 Advisory →
- Fix · GHSA-jp3f-x449-4q75 github.com/mattermost/mattermost/server/v8 (Go) Fixed in 10.11.14 Advisory →
- Fix · GHSA-jp3f-x449-4q75 github.com/mattermost/mattermost/server/v8 (Go) Fixed in 8.0.0-20260318173148-e9ae890a013b Advisory →
- Fix · GHSA-jp3f-x449-4q75 github.com/mattermost/mattermost-server (Go) Fixed in 5.3.2-0.20260318173148-e9ae890a013b Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-6334
- 2026-10-03 Alias added: GHSA-jp3f-x449-4q75
References
More Mattermost Server vulnerabilities
- TI-2025-18933 Arbitrary file read in Mattermost Boards via import & export board archive CVSS 3.1CRITICAL 9.9
- TI-2025-04465 Path Traversal Leading to RCE by Any Authenticated Mattermost User CVSS 3.1CRITICAL 9.9
- TI-2017-14068 An issue was discovered in Mattermost Server before 3.6.2. CVSS 3.1CRITICAL 9.8
- TI-2017-14060 An issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. CVSS 3.1CRITICAL 9.8
- TI-2017-14048 An issue was discovered in Mattermost Server before 4.1.0, 4.0.4, and 3.10.3. CVSS 3.1CRITICAL 9.8
- TI-2025-14360 Arbitrary file read via block duplication in Mattermost Boards CVSS 3.1CRITICAL 9.9
Sources
- CVE-2026-6334 · CVE Program
- CVE-2026-6334 · NVD
- FIRST EPSS
- GHSA-jp3f-x449-4q75 · GitHub Advisory Database · CC BY 4.0
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