{"cve":"CVE-2021-21332","nvd":{"published":"2021-03-26T20:15:11.843","modified":"2026-06-17T03:35:18.940","status":"Modified","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 1.27.0, the password reset endpoint served via Synapse was vulnerable to cross-site scripting (XSS) attacks. The impact depends on the configuration of the domain that Synapse is deployed on, but may allow access to cookies and other browser data, CSRF vulnerabilities, and access to other resources served on the same domain or parent domains. This is fixed in version 1.27.0.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N","score":8.2},"cwes":["CWE-79"],"references":["https://github.com/matrix-org/synapse/commit/e54746bdf7d5c831eabe4dcea76a7626f1de73df","https://github.com/matrix-org/synapse/pull/9200","https://github.com/matrix-org/synapse/releases/tag/v1.27.0","https://github.com/matrix-org/synapse/security/advisories/GHSA-246w-56m2-5899","https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/"],"products":["fedoraproject:fedora","matrix:synapse"],"source":"nvd","synced_at":"2026-10-19T21:17:01.373894544+00:00"},"epss":{"cve":"CVE-2021-21332","score":0.01221,"percentile":0.68706,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-246w-56m2-5899","url":"https://osv.dev/vulnerability/GHSA-246w-56m2-5899","summary":"Cross-site scripting (XSS) vulnerability in the password reset endpoint","modified":"2026-07-08T06:27:41.588536149Z","packages":[{"ecosystem":"PyPI","name":"matrix-synapse","purl":"pkg:pypi/matrix-synapse","ranges":["<1.27.0"],"fixed":["1.27.0"]}]},{"id":"PYSEC-2021-133","url":"https://osv.dev/vulnerability/PYSEC-2021-133","summary":"","modified":"2023-11-08T04:04:41.638851Z","packages":[{"ecosystem":"PyPI","name":"matrix-synapse","purl":"pkg:pypi/matrix-synapse","ranges":["<1.27.0"],"fixed":["1.27.0"]}]}],"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."]}