DoS via URL Previews Rendering Malicious SVGs
Priority LOW 33CWE-754Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub.
Summary
Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to prevent rendering of external SVGs on link embeds which allows unauthenticated users to crash the Mattermost webapp and desktop app via creating an issue or PR on GitHub.. Mattermost Advisory ID: MMSA-2026-00595
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00358 29th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.5.0, 11.4.1, 11.3.2 +2github.com/mattermost/mattermost/server/v8 (Go): 11.4.1, 11.3.2, 11.2.4 +2
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 | 11.4.0 – 11.4.0; 11.3.0 – 11.3.1; 11.2.0 – 11.2.3; 10.11.0 – 10.11.11 | 11.5.0, 11.4.1, 11.3.2, 11.2.4, 10.11.12 | Patch available | CNA |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 11.4.0-rc1 to before 11.4.1 | 11.4.1 | Patch available | GHSA-86vc-mg26-fj6x |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 11.3.0-rc1 to before 11.3.2 | 11.3.2 | Patch available | GHSA-86vc-mg26-fj6x |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 11.2.0-rc1 to before 11.2.4 | 11.2.4 | Patch available | GHSA-86vc-mg26-fj6x |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 8.0.0-20260105080200-d27a2195068d to before 8.0.0-20260217110922-b7d4a1f1f59b | 8.0.0-20260217110922-b7d4a1f1f59b | Patch available | GHSA-86vc-mg26-fj6x |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 10.11.0-rc1 to before 10.11.2 | 10.11.2 | Patch available | GHSA-86vc-mg26-fj6x |
- Mattermost VendorMattermost Affected 11.4.0 – 11.4.0; 11.3.0 – 11.3.1; 11.2.0 – 11.2.3; 10.11.0 – 10.11.11 Fixed in 11.5.0, 11.4.1, 11.3.2, 11.2.4, 10.11.12 Patch available CNA
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 11.4.0-rc1 to before 11.4.1 Fixed in 11.4.1 Patch available GHSA-86vc-mg26-fj6x
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 11.3.0-rc1 to before 11.3.2 Fixed in 11.3.2 Patch available GHSA-86vc-mg26-fj6x
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 11.2.0-rc1 to before 11.2.4 Fixed in 11.2.4 Patch available GHSA-86vc-mg26-fj6x
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 8.0.0-20260105080200-d27a2195068d to before 8.0.0-20260217110922-b7d4a1f1f59b Fixed in 8.0.0-20260217110922-b7d4a1f1f59b Patch available GHSA-86vc-mg26-fj6x
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 10.11.0-rc1 to before 10.11.2 Fixed in 10.11.2 Patch available GHSA-86vc-mg26-fj6x
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | 10.11.0 to before 10.11.12; 11.2.0 to before 11.2.4; 11.3.0 to before 11.3.2; 11.4.0 to before 11.4.1 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.12; 11.2.0 to before 11.2.4; 11.3.0 to before 11.3.2; 11.4.0 to before 11.4.1 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 11.5.0, 11.4.1, 11.3.2, 11.2.4, 10.11.12
- Fix · GHSA-86vc-mg26-fj6x github.com/mattermost/mattermost/server/v8 (Go) Fixed in 11.4.1 Advisory →
- Fix · GHSA-86vc-mg26-fj6x github.com/mattermost/mattermost/server/v8 (Go) Fixed in 11.3.2 Advisory →
- Fix · GHSA-86vc-mg26-fj6x github.com/mattermost/mattermost/server/v8 (Go) Fixed in 11.2.4 Advisory →
- Fix · GHSA-86vc-mg26-fj6x github.com/mattermost/mattermost/server/v8 (Go) Fixed in 8.0.0-20260217110922-b7d4a1f1f59b Advisory →
- Fix · GHSA-86vc-mg26-fj6x github.com/mattermost/mattermost/server/v8 (Go) Fixed in 10.11.2 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-20719
- 2026-10-03 Alias added: GHSA-86vc-mg26-fj6x
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-2026-20719 · CVE Program
- CVE-2026-20719 · NVD
- FIRST EPSS
- GHSA-86vc-mg26-fj6x · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences