CVE-2023-38691 Explained : Impact and Mitigation
Learn about CVE-2023-38691, a medium severity vulnerability in matrix-appservice-bridge allowing unauthorized access to provisioning APIs through improper authentication. Find out the impacted versions and mitigation steps.
This article provides an in-depth analysis of CVE-2023-38691, a vulnerability in matrix-appservice-bridge that allows unauthorized access to provisioning APIs by not verifying the 'sub' parameter of an openID token exchange.
Understanding CVE-2023-38691
CVE-2023-38691 is a vulnerability found in matrix-appservice-bridge, impacting versions 4.0.0 to 8.1.2 and version 9.0.0. It enables unauthorized access to provisioning APIs through improper verification of the 'sub' parameter in an openID token exchange.
What is CVE-2023-38691?
matrix-appservice-bridge is susceptible to an improper authentication vulnerability, allowing a malicious Matrix server to impersonate users by exploiting the 'sub' parameter in the OpenID exchange. This can lead to unauthorized access to provisioning APIs.
The Impact of CVE-2023-38691
The vulnerability poses a medium severity threat with a CVSS base score of 5. It can result in unauthorized provisioning API access by bad actors using a foreign user's MXID.
Technical Details of CVE-2023-38691
CVE-2023-38691 involves the following technical aspects:
Vulnerability Description
The flaw lies in the failure to validate the servername part of the 'sub' parameter in the OpenID exchange, allowing malicious servers to impersonate users and access provisioning APIs.
Affected Systems and Versions
Versions 4.0.0 to 8.1.2 and version 9.0.0 of matrix-appservice-bridge are affected by this vulnerability. Versions 8.1.2 and 9.0.1 have received a patch to address the issue.
Exploitation Mechanism
A bad actor can exploit the vulnerability by utilizing a malicious Matrix server to manipulate the 'sub' parameter, impersonate users, and gain unauthorized access to provisioning APIs.
Mitigation and Prevention
To mitigate the risk associated with CVE-2023-38691, consider the following steps:
Immediate Steps to Take
Disable the provisioning API to prevent unauthorized access until the affected versions are updated.
Long-Term Security Practices
Regularly update matrix-appservice-bridge to the latest secure version to eliminate vulnerabilities.
Patching and Updates
Upgrade to versions 8.1.2 or 9.0.1 of matrix-appservice-bridge, which contain patches to address the authentication vulnerability.