{"schemaVersion":3,"id":"CVE-2021-21274","aliases":["GHSA-2hwx-mjrm-v3g8","PYSEC-2021-132","UBUNTU-CVE-2021-21274","DEBIAN-CVE-2021-21274"],"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, a malicious homeserver could redirect requests to their .well-known file to a large file. This can lead to a denial of service attack where homeservers will consume significantly more resources when requesting the .well-known file of a malicious homeserver. This affects any server which accepts federation requests from untrusted servers. Issue is resolved in version 1.25.0. 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