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Fencer Vulns
medium 5.0

CVE-2023-32323 json

Synapse Outgoing federation to specific hosts can be disabled by sending malicious invites

published 2023-05-24 3 y ago modified 2026-06-17 4 mo ago also GHSA-f3wc-3vxv-xmvr , PYSEC-2023-67 , EUVD-2023-0139

cvss
5.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.0%
EPSS 1.0% chance of exploitation in 30 days, percentile 62%
public exploits
0
none known

Summary

Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. A malicious user on a Synapse homeserver X with permission to create certain state events can disable outbound federation from X to an arbitrary homeserver Y. Synapse instances with federation disabled are not affected. In versions of Synapse up to and including 1.73, Synapse did not limit the size of `invite_room_state`, meaning that it was possible to create an arbitrarily large invite event. Synapse 1.74 refuses to create oversized `invite_room_state` fields. Server operators should upgrade to Synapse 1.74 or newer urgently.

Patch / fix

  • pypi matrix-synapse 1.74.0
  • matrix synapse 1.74.0
  • synapse Alpine 3.24, Alpine 3.23, Alpine 3.22 +4 more 1.74.0-r0

alpine advisories ALPINE-CVE-2023-32323

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-2023-32323 updated cvss 5.0

matrix-synapse: Synapse Outgoing federation to specific hosts can be disabled by sending malicious invites

  • 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
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
21 mo ago

Exploit prediction

0.98% chance of exploitation in the next 30 days, higher than 62% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/matrix-org/synapse/issues/14492 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.0 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:L
NVD 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
GitHub 3.1 5.0 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
pypi matrix-synapse
<1.74.0
1.74.0

Affected products

  • matrix-org synapse

Classification

Weakness
  • CWE-20 Improper Input Validation

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.