CVE-2023-32683 — Synapse is a Matrix protocol homeserver written in Python with the Twisted frame

Synapse is a Matrix protocol homeserver written in Python with the Twisted framework. A discovered oEmbed or image URL can bypass the `url_preview_url_blacklist` setting potentially allowing server side request forgery or bypassing network policies. Impact is limited to IP addres

01What is this vulnerability?

Synapse is a Matrix protocol homeserver written in Python with the Twisted framework. A discovered oEmbed or image URL can bypass the `url_preview_url_blacklist` setting potentially allowing server side request forgery or bypassing network policies. Impact is limited to IP addresses allowed by the `url_preview_ip_range_blacklist` setting (by default this only allows public IPs) and by the limited…

02Affected products

Vendor	Product	Versions
matrix-org	synapse	< 1.85.0

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2023-06-06T18:24:30.457Z
• Last modified: 2025-02-13T16:54:58.218Z

09References

• github.com — https://github.com/matrix-org/synapse/security/advisories/GHSA-98px-6486-j7qc
• github.com — https://github.com/matrix-org/synapse/pull/15601
• lists.fedoraproject.org — https://lists.fedoraproject.org/archives/list/[email protected]…