CVE-2023-38691
5.0 · MEDIUMOverview
CVE-2023-38691 is a medium-severity vulnerability affecting matrix matrix-appservice-bridge. It was published on August 4, 2023 and has a CVSS 3.1 base score of 5.0 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 5.0, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.
Technical Description
matrix-appservice-bridge provides an API for setting up bridges. Starting in version 4.0.0 and prior to versions 8.1.2 and 9.0.1, a malicious Matrix server can use a foreign user's MXID in an OpenID exchange, allowing a bad actor to impersonate users when using the provisioning API. The library does not check that the servername part of the `sub` parameter (containing the user's *claimed* MXID) is the the same as the servername we are talking to. A malicious actor could spin up a server on any given domain, respond with a `sub` parameter according to the user they want to act as and use the resulting token to perform provisioning requests. Versions 8.1.2 and 9.0.1 contain a patch. As a workaround, disable the provisioning API.
Remediation
Check the references section for vendor advisories and patches from matrix. Update matrix-appservice-bridge to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| matrix | matrix-appservice-bridge | >= 4.0.0, < 8.1.2 | Affected |
References
Frequently Asked Questions
What is CVE-2023-38691?
CVE-2023-38691 is a medium-severity vulnerability affecting matrix matrix-appservice-bridge. It was published on August 4, 2023 and has a CVSS 3.1 base score of 5.0 (MEDIUM).
How severe is CVE-2023-38691?
This vulnerability has a CVSS 3.1 base score of 5.0, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.
How do I fix or remediate CVE-2023-38691?
Check the references section for vendor advisories and patches from matrix. Update matrix-appservice-bridge to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2023-38691?
CyberStrike's AI-powered security agents can automatically detect CVE-2023-38691 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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