{"schemaVersion":3,"id":"CVE-2023-39953","aliases":[],"status":"published","duplicateOf":null,"title":null,"description":"user_oidc provides the OIDC connect user backend for Nextcloud, an open-source cloud platform. Starting in version 1.0.0 and prior to version 1.3.3, missing verification of the issuer would have allowed an attacker to perform a man-in-the-middle attack returning corrupted or known token they also have access to. user_oidc 1.3.3 contains a patch. No known workarounds are available.","dates":{"published":"2023-08-10T13:55:19.957Z","modified":"2024-10-03T15:11:48.536Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":4.8,"severity":"medium","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":4.8,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":4.8,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00542,"percentile":0.44471,"severity":"low","asOf":"2026-10-20T00:00:00.000Z","change":{"pp":0,"baselineDate":"2026-09-20T00:00:00.000Z","baselineScore":0.00542},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00542,"percentile":0.44471}],"last30":[{"date":"2026-09-20T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00542,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","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