CVSS 3.1
6.5 mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:NCVE-2023-38691
Medium (6.5) in matrix matrix-appservice-bridge. EPSS 0.5% chance of exploitation in the next 30 days. Fixed in matrix-appservice-bridge 8.1.2, 9.0.1.
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.
Severity
- EPSS
- 0.5% chance of exploitation in the next 30 days; higher than 40% of CVEs (scores of 2026-10-31)
- CWE
- CWE-287
- Published
- Modified
- Record from
- the NVD, synced
Affected
- matrix:matrix-appservice-bridge
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-vc7j-h8xg-fv5x | npm | matrix-appservice-bridge | >=4.0.0 <8.1.2 | 8.1.2 |
| GHSA-vc7j-h8xg-fv5x | npm | matrix-appservice-bridge | >=9.0.0 <9.0.1 | 9.0.1 |
References
- https://github.com/matrix-org/matrix-appservice-bridge/commit/4c6723a5e7beda65cdf1ae5dbb882e8beaac8552
- https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-vc7j-h8xg-fv5x
- https://github.com/matrix-org/matrix-appservice-bridge/commit/4c6723a5e7beda65cdf1ae5dbb882e8beaac8552
- https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-vc7j-h8xg-fv5x