- 6.5MediumCVSS base score
- 2.4%Exploitation in 30 daysEPSS · top 16% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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`).
Timeline
ID reserved
By GitHub_M
- 2 months later
· 2 months later
Published
- 4 years later
· 4 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
| NVDNVD · Modified | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 2.4% · top 16% of all CVEs (9 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.
Affected products
- affected < 1.23.1
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- PyPImatrix-synapseGHSA-hxmp-pqch-c8mm (opens in a new tab)
References
6
- https://github.com/matrix-org/synapse/security/advisories/GHSA-hxmp-pqch-c8mm (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://github.com/matrix-org/synapse/pull/8776 (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/matrix-org/synapse/commit/3ce2f303f15f6ac3dc352298972dc6e04d9b7a8b (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/matrix-org/synapse/blob/develop/CHANGES.md#synapse-1231-2020-12-09 (opens in a new tab)x_refsource_MISCx_transferred
- FEDORA-2020-a2172c484d (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- FEDORA-2020-eeb66c2ece (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2020-0106 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-hxmp-pqch-c8mm (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2020-26257)Record last updated .