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.
github.com/matrix-org/synapse
github.com/matrix-org/synapse/blob/67f9e5293ea6650b2ec284c0b7503f3f3eade94b/docs/changelogs/CHANGES-pre-1.0.md?plain=1#L460
github.com/matrix-org/synapse/issues/4664
github.com/matrix-org/synapse/pull/4315
github.com/matrix-org/synapse/pull/4373
lists.fedoraproject.org/archives/list/[email protected]/message/32Y6KD3OAHCG5P33HC2QEX3NUZOSXCGZ
lists.fedoraproject.org/archives/list/[email protected]/message/VMCLO5PUPBA756UKY72PKUWL4RRM4W6K
matrix.org/blog/2019/01/10/critical-security-update-synapse-0-34-0-1-synapse-0-34-1-1
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
nvd.nist.gov/vuln/detail/CVE-2019-5885