{"cve":"CVE-2023-38691","nvd":{"published":"2023-08-04T17:15:11.063","modified":"2026-06-17T06:10:57.813","status":"Modified","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","score":6.5},"cwes":["CWE-287"],"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"],"products":["matrix:matrix-appservice-bridge"],"source":"nvd","synced_at":"2026-10-19T21:38:35.729974749+00:00"},"epss":{"cve":"CVE-2023-38691","score":0.00466,"percentile":0.40337,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-vc7j-h8xg-fv5x","url":"https://osv.dev/vulnerability/GHSA-vc7j-h8xg-fv5x","summary":"matrix-appservice-bridge doesn't verify the sub parameter of an openId token exhange, allowing unauthorized access to provisioning APIs","modified":"2026-09-10T03:49:57.718797886Z","packages":[{"ecosystem":"npm","name":"matrix-appservice-bridge","purl":"pkg:npm/matrix-appservice-bridge","ranges":[">=4.0.0 <8.1.2"],"fixed":["8.1.2"]},{"ecosystem":"npm","name":"matrix-appservice-bridge","purl":"pkg:npm/matrix-appservice-bridge","ranges":[">=9.0.0 <9.0.1"],"fixed":["9.0.1"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}