CVE intelligence and bounded remediation
CVE-2024-37303 — Synapse is an open-source Matrix homeserver
Synapse is an open-source Matrix homeserver. Synapse before version 1.106 allows, by design, unauthenticated remote participants to trigger a download and caching of remote media from a remote homeserver to the local media repository. Such content then also becomes available for download from the local homeserver in an unauthenticated way. The implication is that unauthenticated remote adversaries can use this functionality to plant problematic content into the media repository. Synapse 1.106 introduces a partial mitigation in the form of new endpoints which require authentication for media downloads. The unauthenticated endpoints will be frozen in a future release, closing the attack vector.
- Severity
- Medium
- CVSS
- 5.3 (3.1)
- Published
- 2024-12-03
- CISA KEV
- Not currently listed
- Ecosystem
- software/application
- Weaknesses
- CWE-306
Affected products
- matrix / synapse
Matched remediation archetype
Authentication bypass and missing authentication
This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.
Check exposure
- Map every affected endpoint and protocol path, including alternate ports, legacy routes, recovery flows, service accounts, and machine-to-machine access.
- Confirm which deployments enable the affected authentication mode and whether the interface is reachable from untrusted networks.
- Review session, token, credential, and proxy trust configuration without attempting account takeover.
Remediate safely
- Apply the supported fix and centralize fail-closed authentication before protected request handling.
- Remove default or embedded credentials, rotate affected secrets and sessions, and bind authentication decisions to the intended audience and channel.
- Add negative tests for alternate routes, malformed or absent credentials, recovery flows, and proxy-derived identity.
Authoritative sources
Complete CVE record and remediation plan
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