{"id":"CVE-2023-39953","aliases":["EUVD-2023-43651","GHSA-xx3h-v363-q36j"],"status":"published","title":"Issuer not verified from obtained token in user_oidc","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.","severity":{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00542,"percentile":0.46007,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-303"],"published":"2023-08-10T13:55:19Z","modified":"2026-10-28T02:30:28Z","products":[{"vendor":"kiteworks","product":"security-advisories"},{"vendor":"nextcloud","product":"security-advisories"},{"vendor":"nextcloud","product":"user_oidc"}],"references":[{"url":"https://github.com/nextcloud/security-advisories/security/advisories/GHSA-xx3h-v363-q36j","tags":["x_refsource_CONFIRM","x_transferred","Patch","Vendor Advisory","advisory"]},{"url":"https://github.com/nextcloud/user_oidc/pull/642","tags":["x_refsource_MISC","x_transferred","Patch","fix"]},{"url":"https://hackerone.com/reports/2021684","tags":["x_refsource_MISC","x_transferred","Permissions Required","web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/39xxx/CVE-2023-39953.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2023-39953","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2023-39953","title":"Issuer not verified from obtained token in user_oidc","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.","status":"published","published":"2023-08-10T13:55:19.957Z","modified":"2024-10-03T15:11:48.536Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-303"],"updated_at":"2026-11-02T14:35:33.462059Z"}],"euvd":[{"id":"EUVD-2023-43651","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.","status":"published","published":"2023-08-10T13:55:19Z","modified":"2024-10-03T15:11:48Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-03T00:27:54.233481Z"}],"nvd":[{"id":"CVE-2023-39953","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.","status":"published","published":"2023-08-10T14:15:15.37Z","modified":"2026-06-17T06:13:01.257Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"secondary"},{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-303"],"updated_at":"2026-11-02T14:08:22.812138Z"}],"osv":[{"id":"CVE-2023-39953","title":"Issuer not verified from obtained token in user_oidc","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.","status":"published","published":"2023-08-10T13:55:19.957Z","modified":"2026-10-28T02:30:28.480537635Z","cvss":[{"version":"3.1","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-303"],"updated_at":"2026-11-02T15:44:33.244128Z"}]}}