CVE-2021-21274

Published: 26 February 2021

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.

Priority

Cvss 3 Severity Score

6.5

Score breakdown

Status

Package	Release	Status
matrix-synapse Launchpad, Ubuntu, Debian	bionic	Needs triage
	focal	Needs triage
	groovy	Ignored (end of life)
	hirsute	Not vulnerable (1.26.0-3)
	jammy	Not vulnerable (1.26.0-3)
	trusty	Does not exist
	upstream	Released (1.25.0-1)
	xenial	Does not exist
	impish	Not vulnerable (1.26.0-3)
	kinetic	Not vulnerable (1.26.0-3)
	lunar	Not vulnerable (1.26.0-3)
	mantic	Not vulnerable (1.26.0-3)

Severity score breakdown

Parameter	Value
Base score	6.5
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	Required
Scope	Unchanged
Confidentiality	None
Integrity impact	None
Availability impact	High
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

References

Join the discussion

Canonical is offering Expanded Security Maintenance

Canonical is offering Ubuntu Expanded Security Maintenance (ESM) for security fixes and essential packages.

Find out more about ESM ›