cbcvebase.
CVE-2021-21274
published 2021-02-26

CVE-2021-21274: Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP…

PriorityP430medium6.5CVSS 3.1
AVNACLPRNUIRSUCNINAH
EPSS
2.16%
80.2th percentile
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. As a workaround the `federation_domain_whitelist` setting can be used to restrict the homeservers communicated with over federation.

Affected

4 ranges
VendorProductVersion rangeFixed in
debianmatrix-synapse< matrix-synapse 1.25.0-1 (forky)matrix-synapse 1.25.0-1 (forky)
fedoraprojectfedora——
matrix-orgsynapse——
matrixsynapse>= 0.99.0 < 1.25.01.25.0

CVSS provenance

nvdv3.16.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
nvdv2.04.3MEDIUMAV:N/AC:M/Au:N/C:N/I:N/A:P
osv6.5MEDIUM
vendor_debian4.3MEDIUM
Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.