{"id":"CVE-2023-38691","state":"PUBLISHED","title":"matrix-appservice-bridge doesn't verify the sub parameter of an openId token exhange, allowing unauthorized access to provisioning APIs","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.","publishedAt":"2023-08-04T16:34:54.312Z","updatedAt":"2024-10-07T13:01:29.642Z","severity":{"score":5,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["matrix-org matrix-appservice-bridge"],"affected":[{"vendor":"matrix-org","product":"matrix-appservice-bridge","versions":[{"version":">= 4.0.0, < 8.1.2","status":"affected"},{"version":"= 9.0.0","status":"affected"}]}],"references":["https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-vc7j-h8xg-fv5x","https://github.com/matrix-org/matrix-appservice-bridge/commit/4c6723a5e7beda65cdf1ae5dbb882e8beaac8552"],"weaknesses":["CWE-287"],"ingestedAt":"2026-10-29T20:06:08.715Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2023/38xxx/CVE-2023-38691.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.1","cveMetadata":{"cveId":"CVE-2023-38691","state":"PUBLISHED","datePublished":"2023-08-04T16:34:54.312Z","dateUpdated":"2024-10-07T13:01:29.642Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2023-07-24T16:19:28.364Z"},"containers":{"cna":{"title":"matrix-appservice-bridge doesn't verify the sub parameter of an openId token exhange, allowing unauthorized access to provisioning APIs","descriptions":[{"lang":"en","value":"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. 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