CVE-2020-26257

medium

Published 2020-12-09 · Modified 2023-11-08

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CVSS v3

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CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS v4 NEW

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not yet in upstream

VIR risk

5.5

Description

Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference "homeserver" implementation of Matrix. 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. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).

Predictions

Exploit likelihood

30%

Patch ETA

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Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here with source_tier=community-verified.

OS impact

Arch Fixed 1 release

Version	Status	Fixed in
—	Fixed	`1.24.0-1`

Debian Fixed 2 releases

Version	Status	Fixed in
sid	Fixed	`1.24.0-1`
forky	Fixed	`1.24.0-1`

Package impact

Ecosystem	Package	Vulnerable	Fixed
PyPI	matrix-synapse	`<1.23.1`	`1.23.1`
PyPI	matrix-synapse	`<3ce2f303f15f6ac3dc352298972dc6e04d9b7a8b\|\|<1.23.1`	`3ce2f303f15f6ac3dc352298972dc6e04d9b7a8b`

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.