{"schemaVersion":3,"id":"CVE-2021-21273","aliases":["GHSA-v936-j8gp-9q3p","PYSEC-2021-131","UBUNTU-CVE-2021-21273","DEBIAN-CVE-2021-21273"],"status":"published","duplicateOf":null,"title":null,"description":"Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.25.0, requests to user provided domains were not restricted to external IP addresses when calculating the key validity for third-party invite events and sending push notifications. This could cause Synapse to make requests to internal infrastructure. The type of request was not controlled by the user, although limited modification of request bodies was possible. For the most thorough protection server administrators should remove the deprecated `federation_ip_range_blacklist` from their settings after upgrading to Synapse v1.25.0 which will result in Synapse using the improved default IP address restrictions. See the new `ip_range_blacklist` and `ip_range_whitelist` settings if more specific control is necessary.","dates":{"published":"2021-02-26T17:25:29.000Z","modified":"2024-08-03T18:09:15.293Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":6.1,"severity":"medium","version":"3.1","versionLabel":"v3.1","source":"NVD","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":3.1,"severity":"low","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N","exploitability":null,"impact":null,"computed":false},{"version":"4.0","versionLabel":"v4.0","source":"OSV · Pypi","score":6.3,"severity":"medium","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","exploitability":null,"impact":null,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Pypi","score":3.1,"severity":"low","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N","exploitability":4.1,"impact":2.3,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Ubuntu","score":6.1,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","exploitability":7.2,"impact":4.5,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Debian","score":6.1,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","exploitability":7.2,"impact":4.5,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":6.1,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","exploitability":null,"impact":null,"computed":false},{"version":"2.0","versionLabel":"v2.0","source":"NVD","score":5.8,"severity":"medium","vector":"AV:N/AC:M/Au:N/C:P/I:P/A:N","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.018,"percentile":0.78177,"severity":"low","asOf":"2026-10-19T00:00:00.000Z","change":{"pp":-0.00899999999999998,"baselineDate":"2026-09-19T00:00:00.000Z","baselineScore":0.01809},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.018,"percentile":0.78177}],"last30":[{"date":"2026-09-19T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.01809,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.018,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.018,"percentile":0.78177}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-601","name":"URL Redirection to Untrusted Site ('Open Redirect')","description":"The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.","type":"weakness","status":"Draft","abstraction":"Base","likelihoodOfExploit":"Low","url":"https://cwe.mitre.org/data/definitions/601.html"}],"affected":[{"vendor":"debian","product":"matrix-synapse","name":"matrix-synapse","label":"matrix-synapse","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/matrix-synapse","purlType":"deb","versions":[{"text":"< 1.25.0-1","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.25.0-1","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"matrix-synapse","name":"matrix-synapse","label":"matrix-synapse","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/matrix-synapse","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"fedoraproject","product":"fedora","name":"fedora","label":"fedora","ecosystem":null,"cpePart":"o","purl":null,"purlType":null,"versions":[{"text":"34","noFixRecorded":false,"fixedIn":null}],"versionsText":"34","eol":{"isEol":true,"eolDate":"2022-06-07T00:00:00.000Z","matchMethod":"cpe","cycle":{"name":"34","label":"34","eolFrom":"2022-06-07T00:00:00.000Z","isLts":false,"isMaintained":false,"latestVersion":null},"product":{"name":"fedora","label":"Fedora Linux","category":"os"}},"hubHref":"/vendor/fedoraproject/fedora"},{"vendor":"matrix-org","product":"synapse","name":"synapse","label":"synapse","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 1.25.0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.25.0","eol":null,"hubHref":"/vendor/matrix-org/synapse"},{"vendor":"matrix","product":"synapse","name":"synapse","label":"synapse","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 1.25.0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 1.25.0","eol":null,"hubHref":"/vendor/matrix/synapse"},{"vendor":"PyPI","product":"matrix-synapse","name":"matrix-synapse","label":"matrix-synapse","ecosystem":"PyPI","cpePart":null,"purl":"pkg:pypi/matrix-synapse","purlType":"pypi","versions":[{"text":"< 30fba6210834a4ecd91badf0c8f3eb278b72e746","noFixRecorded":false,"fixedIn":null},{"text":"< 1.25.0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 30fba6210834a4ecd91badf0c8f3eb278b72e746 | < 1.25.0","eol":null,"hubHref":null}],"affectedCount":6,"eol":{"hasEol":true,"count":1},"references":[{"url":"https://github.com/matrix-org/synapse/releases/tag/v1.25.0","label":"github.com/matrix-org/synapse/releases/tag/v1.25.0","hostname":"github.com","tags":["X Refsource MISC","WEB","REPORT","Third Party Advisory"]},{"url":"https://github.com/matrix-org/synapse/security/advisories/GHSA-v936-j8gp-9q3p","label":"github.com/matrix-org/synapse/security/advisories/GHSA-v936-j8gp-9q3p","hostname":"github.com","tags":["X Refsource CONFIRM","WEB","Advisory","REPORT","Patch","Third Party Advisory"]},{"url":"https://github.com/matrix-org/synapse/pull/8821","label":"github.com/matrix-org/synapse/pull/8821","hostname":"github.com","tags":["X Refsource MISC","WEB","REPORT","Patch","Third Party Advisory"]},{"url":"https://github.com/matrix-org/synapse/commit/30fba6210834a4ecd91badf0c8f3eb278b72e746","label":"github.com/matrix-org/synapse/commit/30fba6210834a4ecd91badf0c8f3eb278b72e746","hostname":"github.com","tags":["X Refsource MISC","WEB","FIX","REPORT","Patch","Third Party Advisory"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/","label":"lists.fedoraproject.org/archives/…","hostname":"lists.fedoraproject.org","tags":["Vendor Advisory","X Refsource FEDORA"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21273","label":"nvd.nist.gov/vuln/detail/CVE-2021-21273","hostname":"nvd.nist.gov","tags":["Advisory"]},{"url":"https://github.com/matrix-org/synapse","label":"github.com/matrix-org/synapse","hostname":"github.com","tags":["PACKAGE"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2021-131.yaml","label":"github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2021-131.yaml","hostname":"github.com","tags":["WEB"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY","label":"lists.fedoraproject.org/archives/…","hostname":"lists.fedoraproject.org","tags":["WEB"]},{"url":"https://ubuntu.com/security/CVE-2021-21273","label":"ubuntu.com/security/CVE-2021-21273","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-21273","label":"www.cve.org/CVERecord?id=CVE-2021-21273","hostname":"www.cve.org","tags":["REPORT"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-21273","label":"security-tracker.debian.org/tracker/CVE-2021-21273","hostname":"security-tracker.debian.org","tags":["Advisory"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2021-02-26T17:25:29.000Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2024-08-03T18:09:15.293Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":25,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-19T15:47:29.644Z","stale":false,"partial":false}}