{"id":"CVE-2020-5261","aliases":["EUVD-2020-0344","GHSA-g6j2-ch25-5mmv"],"status":"published","title":"Missing Token Replay Detection","description":"Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 has a faulty implementation of Token Replay Detection. Token Replay Detection is an important defence in depth measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 is not affected. It has a correct Token Replay Implementation and is safe to use. Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 have a faulty implementation of Token Replay Detection. Token Replay Detection is an important defense measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 and prior versions are not affected. These versions have a correct Token Replay Implementation and are safe to use.","severity":{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.01496,"percentile":0.74407,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-294"],"published":"2020-03-25T01:15:15Z","modified":"2026-10-20T10:54:22Z","fixes":[{"ecosystem":"NuGet","package":"Sustainsys.Saml2","fixed_in":["2.5.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"NuGet","package":"Sustainsys.Saml2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.0.0"},{"fixed":"2.5.0"}]}]},{"source":"osv","ecosystem":"NuGet","package":"Sustainsys.Saml2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.0.0"},{"fixed":"2.5.0"}]}],"versions":["2.0.0","2.1.0","2.2.0","2.3.0","2.4.0"]}],"products":[{"vendor":"simplesamlphp","product":"saml2"},{"vendor":"sustainsys","product":"saml2"}],"references":[{"url":"https://github.com/Sustainsys/Saml2/security/advisories/GHSA-g6j2-ch25-5mmv","tags":["x_refsource_CONFIRM","x_transferred","Third Party Advisory","advisory","web"]},{"url":"https://github.com/Sustainsys/Saml2/commit/e58e0a1aff2b1ead6aca080b7cdced55ee6d5241","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web"]},{"url":"https://github.com/Sustainsys/Saml2/issues/711","tags":["x_refsource_MISC","x_transferred","Issue Tracking","Third Party Advisory","report","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2020-5261","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-g6j2-ch25-5mmv"}],"sources":{"cve":[{"id":"CVE-2020-5261","title":"Missing Token Replay Detection","description":"Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 has a faulty implementation of Token Replay Detection. Token Replay Detection is an important defence in depth measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 is not affected. It has a correct Token Replay Implementation and is safe to use. Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 have a faulty implementation of Token Replay Detection. Token Replay Detection is an important defense measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 and prior versions are not affected. These versions have a correct Token Replay Implementation and are safe to use.","status":"published","published":"2020-03-25T01:15:15Z","modified":"2024-08-04T08:22:09.101Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N","level":"high","assessor":"cna"}],"cwes":["CWE-294"],"updated_at":"2026-11-02T14:35:47.56691Z"}],"euvd":[{"id":"EUVD-2020-0344","description":"Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 has a faulty implementation of Token Replay Detection. Token Replay Detection is an important defence in depth measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 is not affected. It has a correct Token Replay Implementation and is safe to use. Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 have a faulty implementation of Token Replay Detection. Token Replay Detection is an important defense measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 and prior versions are not affected. These versions have a correct Token Replay Implementation and are safe to use.","status":"published","published":"2020-03-25T01:15:15Z","modified":"2024-08-04T08:22:09Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N","level":"high"}],"updated_at":"2026-11-03T03:08:07.28588Z"}],"ghsa":[{"id":"GHSA-g6j2-ch25-5mmv","title":"Missing Token Replay Detection in Saml2 Authentication services for ASP.NET","description":"### Impact\nToken Replay Detection is an important defence in depth measure for Single Sign On solutions. In all previous 2.X versions, the Token Replay Detection is not properly implemented. \n\nNote that version 1.0.1 is not affected. It has a correct Token Replay Implementation and is safe to use.\n\n### Patches\nThe 2.5.0 version is patched.\n\n### Workarounds\nThere are no workarounds with existing versions. Fixing the issue requires code updates.\n\n### References\nhttps://en.wikipedia.org/wiki/Replay_attack\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Comment on #711.\n* Email us at [security@sustainsys.com](mailto:security@susatinsys.com) if you think that there are further security issues.","status":"published","published":"2020-03-25T16:52:49Z","modified":"2023-02-01T05:02:57Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N","level":"high"}],"cwes":["CWE-294"],"updated_at":"2026-11-02T14:36:31.364752Z"}],"nvd":[{"id":"CVE-2020-5261","description":"Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 has a faulty implementation of Token Replay Detection. Token Replay Detection is an important defence in depth measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 is not affected. It has a correct Token Replay Implementation and is safe to use. Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 have a faulty implementation of Token Replay Detection. Token Replay Detection is an important defense measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 and prior versions are not affected. These versions have a correct Token Replay Implementation and are safe to use.","status":"published","published":"2020-03-25T02:15:11.427Z","modified":"2026-06-17T03:21:09.337Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N","level":"high","assessor":"secondary"},{"version":"3.1","score":6.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N","level":"medium","assessor":"primary"},{"version":"2.0","score":4.9,"vector":"AV:N/AC:M/Au:S/C:P/I:P/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-294"],"updated_at":"2026-11-02T14:05:56.580228Z"}],"osv":[{"id":"CVE-2020-5261","description":"Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 has a faulty implementation of Token Replay Detection. Token Replay Detection is an important defence in depth measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 is not affected. It has a correct Token Replay Implementation and is safe to use. Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 have a faulty implementation of Token Replay Detection. Token Replay Detection is an important defense measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 and prior versions are not affected. These versions have a correct Token Replay Implementation and are safe to use.","status":"published","published":"2020-03-25T02:15:11.427Z","modified":"2026-10-20T10:54:22.385779472Z","cvss":[{"version":"3.1","score":6.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N","level":"medium"}],"updated_at":"2026-11-02T15:44:16.936975Z"},{"id":"GHSA-g6j2-ch25-5mmv","title":"Missing Token Replay Detection in Saml2 Authentication services for ASP.NET","description":"### Impact\nToken Replay Detection is an important defence in depth measure for Single Sign On solutions. In all previous 2.X versions, the Token Replay Detection is not properly implemented. \n\nNote that version 1.0.1 is not affected. It has a correct Token Replay Implementation and is safe to use.\n\n### Patches\nThe 2.5.0 version is patched.\n\n### Workarounds\nThere are no workarounds with existing versions. Fixing the issue requires code updates.\n\n### References\nhttps://en.wikipedia.org/wiki/Replay_attack\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Comment on #711.\n* Email us at [security@sustainsys.com](mailto:security@susatinsys.com) if you think that there are further security issues.","status":"published","published":"2020-03-25T16:52:49Z","modified":"2026-07-08T05:59:58.863877488Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N","level":"high"}],"cwes":["CWE-294"],"updated_at":"2026-11-02T15:46:47.472172Z"}]}}