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Denial of service attack via incorrect parameters in Matrix Synapse

Moderate severity GitHub Reviewed Published Dec 9, 2020 in matrix-org/synapse • Updated Feb 2, 2023

Package

pip matrix-synapse (pip)

Affected versions

< 1.23.1

Patched versions

1.23.1

Description

Impact

A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a /send_join, /send_leave, /invite or /exchange_third_party_invite request.

This can lead to a denial of service in which future events will not be correctly sent to other servers over federation.

This affects any server which accepts federation requests from untrusted servers.

Patches

Issue is resolved by matrix-org/synapse#8776.

Workarounds

Homeserver administrators could limit access to the federation API to trusted servers (for example via federation_domain_whitelist).

References

@erikjohnston erikjohnston published to matrix-org/synapse Dec 9, 2020
Reviewed Dec 9, 2020
Published to the GitHub Advisory Database Dec 9, 2020
Published by the National Vulnerability Database Dec 9, 2020
Last updated Feb 2, 2023

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS score

0.160%
(53rd percentile)

Weaknesses

CVE ID

CVE-2020-26257

GHSA ID

GHSA-hxmp-pqch-c8mm

Source code

No known source code
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