PyPI/matrix-synapse CVE-2021-21333: medium 6.1, EPSS 1.35%

HTML injection in email and account expiry notifications

Action: Upgrade matrix-synapse to 1.27.0 or later.

pip install matrix-synapse==1.27.0

Affected

Fixed versions

Sources

• osv: GHSA-c5f8-35qr-q4fm
• https://github.com/matrix-org/synapse/security/advisories/GHSA-c5f8-35qr-q4fm
• https://nvd.nist.gov/vuln/detail/CVE-2021-21333
• https://github.com/matrix-org/synapse/pull/9200
• https://github.com/matrix-org/synapse/commit/e54746bdf7d5c831eabe4dcea76a7626f1de73df
• https://github.com/matrix-org/synapse
• https://github.com/matrix-org/synapse/releases/tag/v1.27.0
• https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2021-134.yaml
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY

CVE-2021-21333 · published 2021-03-26T19:53:04Z · modified 2026-07-08T06:27:41.174374736Z · JSON