CVE-2022-31096 in Discourse
Summary
by MITRE • 06/28/2022
Discourse is an open source discussion platform. Under certain conditions, a logged in user can redeem an invite with an email that either doesn't match the invite's email or does not adhere to the email domain restriction of an invite link. The impact of this flaw is aggravated when the invite has been configured to add the user that accepts the invite into restricted groups. Once a user has been incorrectly added to a restricted group, the user may then be able to view content which that are restricted to the respective group. Users are advised to upgrade to the current stable releases. There are no known workarounds to this issue.
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Analysis
by VulDB Data Team • 07/16/2022
The vulnerability identified as CVE-2022-31096 affects Discourse, an open source discussion platform widely used for community forums and discussion spaces. This security flaw represents a critical access control bypass issue that undermines the platform's user management and group restriction mechanisms. The vulnerability specifically targets the invite redemption process, which is a fundamental component of user onboarding and community management within Discourse. When users attempt to redeem invites, the system should validate that the email address used for redemption matches the email address associated with the invite or adheres to the domain restrictions configured for that specific invite link. The flaw allows authenticated users to circumvent these validation checks, potentially enabling unauthorized access to restricted content and group memberships.
The technical implementation of this vulnerability stems from insufficient input validation during the invite redemption process. When an invite is created with specific email domain restrictions or target email addresses, the system should enforce these constraints during redemption. However, the flaw permits users to submit any valid email address during redemption, regardless of whether it matches the original invite parameters or complies with domain restrictions. This validation failure creates a pathway for privilege escalation where users can gain access to restricted groups that were intended to be exclusive to specific individuals or domain participants. The vulnerability is particularly concerning because it operates within the context of already authenticated users, meaning attackers do not need to bypass authentication mechanisms but can instead exploit weaknesses in authorization controls. This represents a classic case of inadequate access control validation, which aligns with CWE-285: Improper Authorization and potentially CWE-287: Improper Authentication.
The operational impact of this vulnerability extends beyond simple access control bypass to potentially compromise the integrity and confidentiality of restricted content within Discourse communities. When users are incorrectly added to restricted groups through this flaw, they can access sensitive discussions, private messages, and community resources that should only be available to specific participants. This could lead to information disclosure in environments where Discourse is used for internal company communications, confidential project discussions, or community management where access restrictions are critical for maintaining security and privacy. The vulnerability's impact is further amplified when considering that Discourse is commonly used in enterprise environments where such access controls are essential for compliance with data protection regulations and internal security policies. The lack of known workarounds means that organizations cannot implement temporary mitigations while waiting for patches, leaving them vulnerable until the official fixes are applied.
Organizations utilizing Discourse should prioritize immediate upgrades to the current stable releases to address this vulnerability, as recommended by the vendor. The absence of workarounds indicates that this is not a simple configuration issue that can be resolved through administrative settings, but rather a fundamental flaw in the platform's core access control logic. Security teams should also conduct comprehensive audits of their Discourse installations to identify any instances where users may have already exploited this vulnerability to gain unauthorized access to restricted groups. The vulnerability demonstrates the critical importance of validating all user inputs and enforcing strict access control checks, particularly in systems where user management and group permissions are central to security architecture. This issue serves as a reminder of the potential consequences when authentication and authorization mechanisms fail to work in concert to maintain secure access controls, and it highlights the necessity of robust input validation and access control enforcement as fundamental security principles. The vulnerability's classification aligns with ATT&CK technique T1078: Valid Accounts, as it allows legitimate authenticated users to gain access to restricted resources through flawed authorization controls rather than through account compromise or credential theft.