SSRF bypass via IPv4-mapped IPv6 literals
Priority LOW 19CWE-918Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Information disclosure
- Confidentiality · integrity · availability
- Low · None · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-918 and the CVSS impact.
Summary
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation which allows an attacker to perform SSRF attacks against internal services via IPv4-mapped IPv6 literals (e.g., [::ffff:127.0.0.1]).. Mattermost Advisory ID: MMSA-2026-00585
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00172 6th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.4.0, 11.3.1, 11.2.3 +1github.com/mattermost/mattermost/server/v8 (Go): 8.0.0-20260129133647-5d787969c2d5+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 | 11.3.0 – 11.3.0; 11.2.0 – 11.2.2; 10.11.0 – 10.11.10 | 11.4.0, 11.3.1, 11.2.3, 10.11.11 | Patch available | CNA |
| — | github.com/mattermost/mattermost/server/v8 (Go) | before 8.0.0-20260129133647-5d787969c2d5 | 8.0.0-20260129133647-5d787969c2d5 | Patch available | GHSA-gqv7-j2j8-qmwq |
| — | github.com/mattermost/mattermost-server (Go) | before 5.3.2-0.20260129133647-5d787969c2d5 | 5.3.2-0.20260129133647-5d787969c2d5 | Patch available | GHSA-gqv7-j2j8-qmwq |
| — | github.com/mattermost/mattermost-server (Go) | 10.11.0-rc1 to before 10.11.11 | 10.11.11 | Patch available | GHSA-gqv7-j2j8-qmwq |
| — | github.com/mattermost/mattermost-server (Go) | 11.2.0-rc1 to before 11.2.3 | 11.2.3 | Patch available | GHSA-gqv7-j2j8-qmwq |
| — | github.com/mattermost/mattermost-server (Go) | 11.3.0-rc1 to before 11.3.1 | 11.3.1 | Patch available | GHSA-gqv7-j2j8-qmwq |
- Mattermost VendorMattermost Affected 11.3.0 – 11.3.0; 11.2.0 – 11.2.2; 10.11.0 – 10.11.10 Fixed in 11.4.0, 11.3.1, 11.2.3, 10.11.11 Patch available CNA
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected before 8.0.0-20260129133647-5d787969c2d5 Fixed in 8.0.0-20260129133647-5d787969c2d5 Patch available GHSA-gqv7-j2j8-qmwq
- github.com/mattermost/mattermost-server (Go) Vendor— Affected before 5.3.2-0.20260129133647-5d787969c2d5 Fixed in 5.3.2-0.20260129133647-5d787969c2d5 Patch available GHSA-gqv7-j2j8-qmwq
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 10.11.0-rc1 to before 10.11.11 Fixed in 10.11.11 Patch available GHSA-gqv7-j2j8-qmwq
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 11.2.0-rc1 to before 11.2.3 Fixed in 11.2.3 Patch available GHSA-gqv7-j2j8-qmwq
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 11.3.0-rc1 to before 11.3.1 Fixed in 11.3.1 Patch available GHSA-gqv7-j2j8-qmwq
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | 10.11.0 to before 10.11.11; 11.2.0 to before 11.2.3; 11.3.0 to before 11.3.1 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.11; 11.2.0 to before 11.2.3; 11.3.0 to before 11.3.1 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 11.4.0, 11.3.1, 11.2.3, 10.11.11
- Fix · GHSA-gqv7-j2j8-qmwq github.com/mattermost/mattermost/server/v8 (Go) Fixed in 8.0.0-20260129133647-5d787969c2d5 Advisory →
- Fix · GHSA-gqv7-j2j8-qmwq github.com/mattermost/mattermost-server (Go) Fixed in 5.3.2-0.20260129133647-5d787969c2d5 Advisory →
- Fix · GHSA-gqv7-j2j8-qmwq github.com/mattermost/mattermost-server (Go) Fixed in 10.11.11 Advisory →
- Fix · GHSA-gqv7-j2j8-qmwq github.com/mattermost/mattermost-server (Go) Fixed in 11.2.3 Advisory →
- Fix · GHSA-gqv7-j2j8-qmwq github.com/mattermost/mattermost-server (Go) Fixed in 11.3.1 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-2455
- 2026-10-03 Alias added: GHSA-gqv7-j2j8-qmwq
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-2026-2455 · CVE Program
- CVE-2026-2455 · NVD
- FIRST EPSS
- GHSA-gqv7-j2j8-qmwq · GitHub Advisory Database · CC BY 4.0
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