CVE-2022-39200: Signature checks not applied to some retrieved missing events

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-09-12 · updated 2026-06-17
Weakness: CWE-347

Description

Dendrite is a Matrix homeserver written in Go. In affected versions events retrieved from a remote homeserver using the `/get_missing_events` path did not have their signatures verified correctly. This could potentially allow a remote homeserver to provide invalid/modified events to Dendrite via this endpoint. Note that this does not apply to events retrieved through other endpoints (e.g. `/event`, `/state`) as they have been correctly verified. Homeservers that have federation disabled are not vulnerable. The problem has been fixed in Dendrite 0.9.8. Users are advised to upgrade. There are no known workarounds for this issue.

Affected products

matrix-org dendrite: before 0.9.8 — fixed in 0.9.8

How to fix

Upgrade to a fixed version: matrix-org dendrite 0.9.8. Check the vendor advisory for mitigations.

References

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