CVE-2023-32683
Synapse has URL deny list bypass via oEmbed and image URLs when generating previews
Description
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 information returned to the client: 1. For discovered oEmbed URLs, any non-JSON response or a JSON response which includes non-oEmbed information is discarded. 2. For discovered image URLs, any non-image response is discarded. Systems which have URL preview disabled (via the `url_preview_enabled` setting) or have not configured a `url_preview_url_blacklist` are not affected. This issue has been addressed in version 1.85.0. Users are advised to upgrade. User unable to upgrade may also disable URL previews.
How to fix CVE-2023-32683
To remediate CVE-2023-32683, upgrade the affected package to a fixed version below.
- —upgrade to 1.90.0-1 or later
- —upgrade to 1.85.0 or later
- —upgrade to 1.85.0 or later
Is CVE-2023-32683 being exploited?
Low — EPSS is 0.3%, meaning exploitation activity has not been observed at scale.
Affected packages (3)
- from 0, < 1.90.0-1
- from 0, < 1.85.0
- from 0, < 1.85.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N |
| osv | CVSS 3.1 | LOW3.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N |