Matrix Synapse before 0.34.0.1, when the macaroon_secret_key authentication parameter is...

Vulnerability Description

Matrix Synapse before 0.34.0.1, when the macaroon_secret_key authentication parameter is not set, uses a predictable value to derive a secret key and other secrets which could allow remote attackers to impersonate users.

References

• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/32Y6KD3OAHCG5P33HC2QEX3NUZOSXCGZ/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VMCLO5PUPBA756UKY72PKUWL4RRM4W6K/
• https://matrix.org/blog/2019/01/10/critical-security-update-synapse-0-34-0-1-synapse-0-34-1-1/
• https://matrix.org/blog/2019/01/15/further-details-on-critical-security-update-in-synapse-affecting-all-versions-prior-to-0-34-1-cve-2019-5885/