Vulnerability · Published Aug 4, 2023 · Assigned by GitHub_M
CVE-2023-38691matrix-appservice-bridge doesn't verify the sub parameter of an openId token exhange, allowing unauthorized access to provisioning APIs
Medium 5.0
In plain English
A medium-severity improper authentication in matrix-appservice-bridge from matrix-org. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | matrix-appservice-bridge | 8.1.2 | GHSA-vc7j-h8xg-fv5x |
| npm | matrix-appservice-bridge | 9.0.1 | GHSA-vc7j-h8xg-fv5x |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| matrix-org | matrix-appservice-bridge | >= 4.0.0, < 8.1.2= 9.0.0 |
Weakness: CWE-287 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N