CVE-2023-38691: medium-severity vulnerability in matrix-org matrix-appservice-bridge
matrix-appservice-bridge doesn't verify the sub parameter of an openId token exhange, allowing unauthorized access to provisioning APIs
Published · Updated
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13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5epss 0.5%
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.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N
Affected products
matrix-org · matrix-appservice-bridgeRelated CVEs — matrix-org matrix-appservice-bridge
In the same product, most dangerous first.