CVE-2022-1002 in Mattermost
Summary
by MITRE • 03/18/2022
Mattermost 6.3.0 and earlier fails to properly sanitize the HTML content in the email invitation sent to guest users, which allows registered users with special permissions to invite guest users to inject unescaped HTML content in the email invitations.
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Analysis
by VulDB Data Team • 03/23/2022
This vulnerability exists in Mattermost versions 6.3.0 and earlier where the email invitation system fails to properly sanitize HTML content when sending invitations to guest users. The flaw allows registered users with specific administrative permissions to inject malicious HTML content into email invitations that are then delivered to guest users. The vulnerability stems from insufficient input validation and output escaping mechanisms within the email generation and sending process. When a privileged user sends an invitation to a guest, the system does not adequately filter or escape HTML characters in the invitation content, creating an environment where malicious code can be executed during email rendering.
The technical implementation of this vulnerability involves the email invitation system not properly implementing HTML sanitization before embedding user-supplied content into email templates. This represents a classic cross-site scripting vulnerability that occurs in the email context rather than web browser context. The vulnerability is particularly dangerous because it operates at the email delivery level where guest users are exposed to potentially malicious content simply by receiving the invitation email. Users with special permissions such as team administrators or system managers can exploit this flaw to inject scripts, malicious links, or other HTML content that executes when the email is rendered by the recipient's email client.
The operational impact of this vulnerability extends beyond simple HTML injection as it can enable several attack vectors including phishing attempts, credential harvesting, and malicious payload delivery. Guest users who receive invitations containing malicious HTML content may unknowingly execute scripts that steal session cookies, redirect them to malicious websites, or perform other harmful actions. The vulnerability also enables social engineering attacks where attackers can craft convincing invitation emails that appear legitimate but contain hidden malicious content. This creates a significant risk for organizations using Mattermost as it allows attackers to potentially compromise guest user accounts or use the platform as a vector for broader attacks against the organization's security infrastructure.
This vulnerability maps to CWE-79 Cross-Site Scripting in the Common Weakness Enumeration catalog, specifically representing a case where untrusted data is improperly sanitized in email contexts. The attack pattern aligns with ATT&CK technique T1566.001 Phishing as it enables the creation of malicious email invitations that can trick users into executing harmful content. Organizations should implement immediate mitigations including upgrading to Mattermost versions 6.3.1 or later where this vulnerability has been patched, implementing email content filtering rules, and establishing strict access controls for users who can send invitations. Additionally, organizations should consider implementing email security solutions that can detect and block malicious HTML content in email invitations and conduct regular security awareness training for administrators who have permission to invite guest users.