PyPi: Matrix-Synapse

CVE-2021-21274

Safety vulnerability ID: 39662

This vulnerability was reviewed by experts

The information on this page was manually curated by our Cybersecurity Intelligence Team.

Created at Feb 26, 2021 Updated at Dec 11, 2024
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Advisory

Matrix-synapse 1.25.0 includes a fix for CVE-2021-21274: Denial of service attack via .well-known lookups.
https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8

Affected package

matrix-synapse

Latest version: 1.121.1

Homeserver for the Matrix decentralised comms protocol

Affected versions

Fixed versions

Vulnerability changelog

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. See CVE-2021-21274.


CONFIRM:https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8: https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8
MISC:https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6: https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6
MISC:https://github.com/matrix-org/synapse/pull/8950: https://github.com/matrix-org/synapse/pull/8950
MISC:https://github.com/matrix-org/synapse/releases/tag/v1.25.0: https://github.com/matrix-org/synapse/releases/tag/v1.25.0

Resources

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Severity Details

CVSS Base Score

MEDIUM 6.5

CVSS v3 Details

MEDIUM 6.5
Attack Vector (AV)
NETWORK
Attack Complexity (AC)
LOW
Privileges Required (PR)
NONE
User Interaction (UI)
REQUIRED
Scope (S)
UNCHANGED
Confidentiality Impact (C)
NONE
Integrity Impact (I)
NONE
Availability Availability (A)
HIGH

CVSS v2 Details

MEDIUM 4.3
Access Vector (AV)
NETWORK
Access Complexity (AC)
MEDIUM
Authentication (Au)
NONE
Confidentiality Impact (C)
NONE
Integrity Impact (I)
NONE
Availability Impact (A)
PARTIAL