CVE-2020-26257
Denial of service attack via incorrect parameters in Matrix Synapse
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`).
How to fix CVE-2020-26257
To remediate CVE-2020-26257, upgrade the affected package to a fixed version below.
- —upgrade to 1.24.0-1 or later
- —upgrade to 1.23.1 or later
- —upgrade to 3ce2f303f15f6ac3dc352298972dc6e04d9b7a8b or later
Is CVE-2020-26257 being exploited?
Low — EPSS is 0.4%, meaning exploitation activity has not been observed at scale.
Affected packages (3)
- from 0, < 1.24.0-1
- from 0, < 1.23.1
- from 0, < 3ce2f303f15f6ac3dc352298972dc6e04d9b7a8b | from 0, < 1.23.1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
| osv | CVSS 3.1 | MEDIUM6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |