Is CVE-2023-38691 actively exploited?

No active exploitation of CVE-2023-38691 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2023-38691 be exploited remotely?

Yes. CVE-2023-38691 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2023-38691?

CVE-2023-38691 has a CVSS score of 6.5 (MEDIUM).

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MEDIUM

CVE-2023-38691

CWE-287Published: August 4, 2023· Updated: Jun 17, 2026

6.5

CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2023-38691 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in complete confidentiality breach (data exposure), with a CVSS base score of 6.5.

From a weakness classification perspective (CWE-287): Authentication bypass vulnerabilities allow attackers to access protected resources without valid credentials.