CVE-2020-26257: Denial of service attack via incorrect parameters to federation APIs
First published: Wed Dec 09 2020(Updated: )
### Impact 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. ### Patches Issue is resolved by https://github.com/matrix-org/synapse/pull/8776. ### Workarounds Homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).
Credit: security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| pip/matrix-synapse | <1.23.1 | 1.23.1 |
| Matrix Synapse | <1.23.1 | |
| Fedora | =32 | |
| Fedora | =33 |
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Reference Links
- https://github.com/matrix-org/synapse/blob/develop/CHANGES.md#synapse-1231-2020-12-09
- https://github.com/matrix-org/synapse/commit/3ce2f303f15f6ac3dc352298972dc6e04d9b7a8b
- https://github.com/matrix-org/synapse/pull/8776
- https://github.com/matrix-org/synapse/security/advisories/GHSA-hxmp-pqch-c8mm
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DBTIU3ZNBFWZ56V4X7JIAD33V5H2GOMC/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QR4MMYZKX5N5GYGH4H5LBUUC5TLAFHI7/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QR4MMYZKX5N5GYGH4H5LBUUC5TLAFHI7/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DBTIU3ZNBFWZ56V4X7JIAD33V5H2GOMC/
- https://nvd.nist.gov/vuln/detail/CVE-2020-26257
- https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2020-236.yaml
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DBTIU3ZNBFWZ56V4X7JIAD33V5H2GOMC
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QR4MMYZKX5N5GYGH4H5LBUUC5TLAFHI7
- https://github.com/advisories/GHSA-hxmp-pqch-c8mm (Advisory)
Frequently Asked Questions
What is the severity of CVE-2020-26257?
CVE-2020-26257 has a severity rating that can lead to Denial of Service attacks.
How do I fix CVE-2020-26257?
To fix CVE-2020-26257, update your Matrix Synapse to version 1.23.1 or later.
What software is affected by CVE-2020-26257?
CVE-2020-26257 affects Matrix Synapse versions prior to 1.23.1, as well as Fedora 32 and 33.
What causes CVE-2020-26257?
CVE-2020-26257 is caused by a malicious or poorly-implemented homeserver injecting malformed events by specifying a different room ID.
Can CVE-2020-26257 lead to data breaches?
CVE-2020-26257 primarily leads to denial of service rather than direct data breaches.
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