CVE intelligence and bounded remediation
CVE-2023-43796 — Matrix Synapse security vulnerability
Synapse is an open-source Matrix homeserver Prior to versions 1.95.1 and 1.96.0rc1, cached device information of remote users can be queried from Synapse. This can be used to enumerate the remote users known to a homeserver. System administrators are encouraged to upgrade to Synapse 1.95.1 or 1.96.0rc1 to receive a patch. As a workaround, the `federation_domain_whitelist` can be used to limit federation traffic with a homeserver.
- Severity
- Medium
- CVSS
- 5.3 (3.1)
- Published
- 2023-10-31
- CISA KEV
- Not currently listed
- Ecosystem
- software/application
- Weaknesses
- CWE-200
Affected products
- matrix / synapse
- fedoraproject / fedora / 38
- fedoraproject / fedora / 39
Matched remediation archetype
Information disclosure and sensitive data exposure
This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.
Check exposure
- Trace sensitive data through responses, errors, logs, metrics, traces, caches, exports, files, backups, and client bundles.
- Identify affected subjects, tenants, retention windows, access controls, and downstream copies without opening unnecessary sensitive records.
- Review metadata, timing, status, length, and existence signals as well as direct content disclosure.
Remediate safely
- Minimize collection and output, apply field-level authorization and redaction at a centralized boundary, and return generic external errors.
- Remove secrets and sensitive data from logs, artifacts, URLs, caches, and client-side bundles; rotate credentials that may have been exposed.
- Update the affected component and add synthetic-data tests for response, error, observability, and export paths.
Authoritative sources
Complete CVE record and remediation plan
The detailed catalog view below loads this exact record, its source evidence, and the full seven-phase agentic change plan.