CVSS 3.1
7.5 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HCVE-2020-26890
High (7.5). EPSS 3.0% chance of exploitation in the next 30 days. Fixed in matrix-synapse 1.20.0.
Matrix Synapse before 1.20.0 erroneously permits non-standard NaN, Infinity, and -Infinity JSON values in fields of m.room.member events, allowing remote attackers to execute a denial of service attack against the federation and common Matrix clients. If such a malformed event is accepted into the room's state, the impact is long-lasting and is not fixed by an upgrade to a newer version, requiring the event to be manually redacted instead. Since events are replicated to servers of other room members, the impact is not constrained to the server of the event sender.
Severity
- EPSS
- 3.0% chance of exploitation in the next 30 days; higher than 87% of CVEs (scores of 2026-10-31)
- CWE
- CWE-20
- Published
- Modified
- Record from
- the NVD, synced
Affected
- fedoraproject:fedora
- matrix:synapse
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-4mp3-385r-v63f | PyPI | matrix-synapse | <1.20.0 | 1.20.0 |
| PYSEC-2020-237 | PyPI | matrix-synapse | <1.20.0 | 1.20.0 |
References
- https://github.com/matrix-org/synapse/security/advisories/GHSA-4mp3-385r-v63f
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/G7YXMMYQP46PYL664JQUXCA3LPBJU7DQ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U34DPP4ZLOEDUY2ZCWOHQPU5GA5LYNUQ/
- https://github.com/matrix-org/synapse/security/advisories/GHSA-4mp3-385r-v63f
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/G7YXMMYQP46PYL664JQUXCA3LPBJU7DQ/