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Fencer Vulns
medium 5.3

CVE-2023-43796 json

Synapse vulnerable to leak of remote user device information

published 2023-10-31 3 y ago modified 2026-09-10 1 mo ago also GHSA-mp92-3jfm-3575 , PYSEC-2023-230 , EUVD-2023-0136

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.2%
EPSS 1.2% chance of exploitation in 30 days, percentile 68%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi matrix-synapse 1.95.1
  • matrix synapse 1.95.1
  • 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-2023-43796

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 1.95.1-1.1

opensuse advisories openSUSE-SU-2024:13392-1

  • synapse Alpine 3.24, Alpine 3.23, Alpine 3.22 +4 more 1.95.1-r0

alpine advisories ALPINE-CVE-2023-43796

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-2023-43796 updated cvss 5.3

net-im/synapse: Leak of remote user device information

  • 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

Exploit prediction

1.20% chance of exploitation in the next 30 days, higher than 68% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
OSV 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
pypi matrix-synapse
<1.95.1
1.95.1

Affected products

  • matrix-org synapse

Classification

Weakness
  • CWE-200 Exposure of Sensitive Information to an Unauthorized Actor

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.