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Fencer Vulns
low 3.5

CVE-2023-32683 json

URL deny list bypass via oEmbed and image URLs when generating previews in Synapse

published 2023-06-06 3 y ago modified 2026-06-17 4 mo ago also GHSA-98px-6486-j7qc , PYSEC-2023-85 , EUVD-2023-0141

cvss
3.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 49%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi matrix-synapse 1.85.0
  • matrix synapse 1.85.0
  • matrix-synapse Ubuntu Pro 18.04 LTS 0.24.0+dfsg-1ubuntu0.1~esm4
  • matrix-synapse Ubuntu Pro 20.04 LTS 1.11.0-1ubuntu0.1~esm2
  • matrix-synapse Ubuntu Pro 22.04 LTS 1.53.0-1ubuntu0.1~esm2

ubuntu advisories UBUNTU-CVE-2023-32683

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • matrix-synapse openSUSE Tumbleweed 1.85.2-1.1

opensuse advisories openSUSE-SU-2024:13039-1

  • synapse Alpine 3.24, Alpine 3.23, Alpine 3.22 +4 more 1.85.1-r0

alpine advisories ALPINE-CVE-2023-32683

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2023-32683 updated cvss 3.1

matrix-synapse: URL deny list bypass via oEmbed and image URLs when generating previews

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
22 mo ago

Exploit prediction

0.60% chance of exploitation in the next 30 days, higher than 49% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 3.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
NVD 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
GitHub 3.1 3.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
pypi matrix-synapse
<1.85.0
1.85.0

Affected products

  • matrix-org synapse

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.