CVE-2026-6333 json
SSRF via Host Header Spoofing in Custom Slash Commands
published 2026-05-18 5 mo ago modified 2026-10-14 25 d ago also GHSA-vqp5-2mrp-qqxg , GO-2026-5671 , EUVD-2026-30755
- cvss
- 3.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.1%
- EPSS 0.1% chance of exploitation in 30 days, percentile 3%
- public exploits
- 0
- none known
Summary
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate the Host header when constructing response URLs for custom slash commands which allows an authenticated attacker to redirect slash command responses to an attacker-controlled server via a spoofed Host header.. Mattermost Advisory ID: MMSA-2026-00582
Patch / fix
- go github.com/mattermost/mattermost/server/v8 8.0.0-20260325160634-e738016c5920, 10.11.14, 11.5.2
- go github.com/mattermost/mattermost-server 5.3.2-0.20260325160634-e738016c5920, 10.11.14+incompatible, 11.5.2+incompatible
- Mattermost Mattermost 10.11.14, 11.5.2, 11.6.0
- govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
opensuse advisories openSUSE-SU-2026:21483-1
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 5 mo ago
Exploit prediction
0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 3.5 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N |
| NVD | 3.1 | 5.0 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N |
| GitHub | 3.1 | 3.5 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/mattermost/mattermost/server/v8 | >=11.5.0, <11.5.2 >=10.11.0, <10.11.14 <8.0.0-20260325160634-e738016c5920 |
11.5.2 10.11.14 8.0.0-20260325160634-e738016c5920 |
| go | github.com/mattermost/mattermost-server | <5.3.2-0.20260325160634-e738016c5920 >=10.11.0+incompatible, <10.11.14+incompatible >=11.5.0+incompatible, <11.5.2+incompatible |
5.3.2-0.20260325160634-e738016c5920 10.11.14+incompatible 11.5.2+incompatible |
| 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-918 Server-Side Request Forgery
References
Sources
- CVE List CVE-2026-6333
- GitHub Advisory GHSA-vqp5-2mrp-qqxg
- NVD CVE-2026-6333
- OSV GO-2026-5671
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