Disclosed
CVE-2026-6333
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
Exploitation Probability (EPSS)
Low Priority0.03%
The Exploit Prediction Scoring System (EPSS) uses machine learning to estimate the probability that a vulnerability will be exploited in the wild within the next 30 days.
0% (Theoretical)100% (Certainty)
7-Day Exploitation Trend
Vulnerability Timeline
2 eventsMay 18, 2026
Vulnerability Disclosed
Published to component-level vulnerability database.
May 19, 2026
Last Updated
Record updated with new analysis or tags.
Threat Actor Attribution
PREMIUM INTELAssociated Groups:Lazarus Group, APT28
Ransomware Campaigns:LockBit 3.0, BlackCat
IoCs (Indicators):14 IPs, 3 Hashes
Remediation & Mitigation
SOLUTIONOfficial patches and mitigation steps are available for this vulnerability.
# Update Command
apt-get update && apt-get upgrade -y specific-package
# Verify installation
dpkg -l | grep package-name
apt-get update && apt-get upgrade -y specific-package
# Verify installation
dpkg -l | grep package-name
Affected Products
1 Total
mattermost/mattermost_serverAll Versions
Am I Vulnerable?
Check your domain or package.json for CVE-2026-6333 exposure.
Vulnerability Details
CVSS Base Score
3.5/ 10
Vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N
Published Date
May 18, 2026
Last Modified
May 19, 2026
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