CVE-2026-6333
LOW 3.5Mattermost 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
NO EXPLOITATION SIGNALS
No known exploitation, public exploit, or elevated probability at this time. Track for changes.
Exploitation likelihood
0.1%chance of exploitation in 30 days · 3rd percentile
○ In CISA KEV
○ Public exploit / PoC
Impact if exploited
3.5CVSS 3.1 · LOW
- ConfidentialityNone
- IntegrityLow
- AvailabilityNone
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ⚠Privileges: Requires a low-privilege account
- ✓User interaction: No user interaction needed
- ⚠Complexity: Needs a race window or specific setup
✓ lowers the bar for an attacker · ⚠ raises it
Weakness (CWE)
- CWE-918: Server-side request forgery (SSRF)
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N