GHSA-f3wc-3vxv-xmvr

Suggest an improvement
Source
https://github.com/advisories/GHSA-f3wc-3vxv-xmvr
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2023/05/GHSA-f3wc-3vxv-xmvr/GHSA-f3wc-3vxv-xmvr.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-f3wc-3vxv-xmvr
Aliases
Published
2023-05-24T17:28:26Z
Modified
2024-09-24T15:45:41.893714Z
Severity
  • 5.0 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:L CVSS Calculator
  • 5.3 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:L CVSS Calculator
Summary
Synapse Outgoing federation to specific hosts can be disabled by sending malicious invites
Details

Impact

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.

Details

The Matrix protocol allows homeservers to provide an invite_room_state field on a room invite containing a summary of room state. In versions of Synapse up to and including v1.73.0, Synapse did not limit the size of invite_room_state, meaning that it was possible to create an arbitrarily large invite event.

An attacker with an account on a vulnerable Synapse homeserver X could exploit this by having X create an over-sized invite event in a room with a user from another homeserver Y. Once acknowledged by the invitee's homeserver, the invite event would be sent in a batch of events to Y. If the malicious invite is so large that the entire batch is rejected as too large, X's outgoing traffic to Y would become "stuck", meaning that messages and state events created by X would remain unseen by Y.

Patches

Synapse 1.74 refuses to create oversized invite_room_state fields. Server operators should upgrade to Synapse 1.74 or newer urgently.

Workarounds

There are no robust workarounds.

This attack needs an account on Synapse homeserver X to deny federation from X to another homeserver Y. As a partial mitigation, Synapse operators can disable open registration to limit the ability of attackers to create new accounts on homeserver X.

If homeserver X has been attacked in this way, restarting it will resume outgoing federation by entering "catchup mode". For catchup mode to ignore the oversized invites, every attacked room must have a correctly-sized event sent by X which is newer than any oversized invite. This is difficult to arrange, and does not prevent the attacker from repeating their attack.

References

  • https://github.com/matrix-org/synapse/issues/14492 was caused by this issue.
  • https://github.com/matrix-org/synapse/issues/14642 includes the patch described above.

For more information

If you have any questions or comments about this advisory, e-mail us at security@matrix.org.

Database specific 
{
    "nvd_published_at": "2023-05-26T14:15:10Z",
    "cwe_ids": [
        "CWE-20"
    ],
    "severity": "MODERATE",
    "github_reviewed": true,
    "github_reviewed_at": "2023-05-24T17:28:26Z"
}
References

Affected packages

PyPI / matrix-synapse

Package

Name
matrix-synapse
View open source insights on deps.dev
Purl
pkg:pypi/matrix-synapse

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.74.0

Affected versions

0.*

0.33.5
0.33.5.1
0.33.6rc1
0.33.6
0.33.7rc1
0.33.7rc2
0.33.7
0.33.8rc2
0.33.8
0.33.9
0.34.0rc1
0.34.0rc2
0.34.0
0.34.0.1
0.34.1.1
0.99.0rc1
0.99.0rc2
0.99.0rc3
0.99.0rc4
0.99.0
0.99.1rc1
0.99.1rc2
0.99.1
0.99.1.1
0.99.2rc1
0.99.2
0.99.3rc1
0.99.3
0.99.3.1
0.99.3.2
0.99.4rc1
0.99.4
0.99.5rc1
0.99.5
0.99.5.1
0.99.5.2

1.*

1.0.0rc1
1.0.0rc2
1.0.0rc3
1.0.0
1.1.0rc1
1.1.0rc2
1.1.0
1.2.0rc1
1.2.0rc2
1.2.0
1.2.1
1.3.0rc1
1.3.0
1.3.1
1.4.0rc1
1.4.0rc2
1.4.0
1.4.1rc1
1.4.1
1.5.0rc1
1.5.0rc2
1.5.0
1.5.1
1.6.0rc1
1.6.0rc2
1.6.0
1.6.1
1.7.0rc1
1.7.0rc2
1.7.0
1.7.1
1.7.2
1.7.3
1.8.0rc1
1.8.0
1.9.0.dev1
1.9.0.dev2
1.9.0rc1
1.9.0
1.9.1
1.10.0rc1
1.10.0rc2
1.10.0rc3
1.10.0rc5
1.10.0
1.10.1
1.11.0rc1
1.11.0
1.11.1
1.12.0rc1
1.12.0
1.12.1rc1
1.12.1
1.12.2
1.12.3
1.12.4rc1
1.12.4
1.13.0rc1
1.13.0rc2
1.13.0rc3
1.13.0
1.14.0rc1
1.14.0rc2
1.14.0
1.15.0rc1
1.15.0
1.15.1
1.15.2
1.16.0rc1
1.16.0rc2
1.16.0
1.16.1
1.17.0rc1
1.17.0
1.18.0rc1
1.18.0rc2
1.18.0
1.19.0rc1
1.19.0
1.19.1rc1
1.19.1
1.19.2
1.19.3
1.20.0rc1
1.20.0rc2
1.20.0rc3
1.20.0rc4
1.20.0rc5
1.20.0
1.20.1
1.21.0rc1
1.21.0rc2
1.21.0rc3
1.21.0
1.21.1
1.21.2
1.22.0rc1
1.22.0rc2
1.22.0
1.22.1
1.23.0rc1
1.23.0
1.23.1
1.24.0rc1
1.24.0rc2
1.24.0
1.25.0rc1
1.25.0
1.26.0rc1
1.26.0rc2
1.26.0
1.27.0rc1
1.27.0rc2
1.27.0
1.28.0rc1
1.28.0
1.29.0rc1
1.29.0
1.30.0rc1
1.30.0
1.30.1
1.31.0rc1
1.31.0
1.32.0rc1
1.32.0
1.32.1
1.32.2
1.33.0rc1
1.33.0rc2
1.33.0
1.33.1
1.33.2
1.34.0rc1
1.34.0
1.35.0rc1
1.35.0rc2
1.35.0rc3
1.35.0
1.35.1
1.36.0rc1
1.36.0rc2
1.36.0
1.37.0rc1
1.37.0
1.37.1rc1
1.37.1
1.38.0rc1
1.38.0rc2
1.38.0rc3
1.38.0
1.38.1
1.39.0rc1
1.39.0rc2
1.39.0rc3
1.39.0
1.40.0rc1
1.40.0rc2
1.40.0rc3
1.40.0
1.41.0rc1
1.41.0
1.41.1
1.42.0rc1
1.42.0rc2
1.42.0
1.43.0rc1
1.43.0rc2
1.43.0
1.44.0rc1
1.44.0rc2
1.44.0rc3
1.44.0
1.45.0rc1
1.45.0rc2
1.45.0
1.45.1
1.46.0rc1
1.46.0
1.47.0rc1
1.47.0rc2
1.47.0rc3
1.47.0
1.47.1
1.48.0rc1
1.48.0
1.49.0rc1
1.49.0
1.49.2
1.50.0rc1
1.50.0rc2
1.50.0
1.50.1
1.50.2
1.51.0rc1
1.51.0rc2
1.51.0
1.52.0rc1
1.52.0
1.53.0rc1
1.53.0
1.54.0rc1
1.54.0
1.55.0rc1
1.55.0
1.55.1
1.55.2
1.56.0rc1
1.56.0
1.57.0rc1
1.57.0
1.57.1
1.58.0rc2
1.58.0
1.58.1
1.59.0rc1
1.59.0rc2
1.59.0
1.59.1
1.60.0rc1
1.60.0rc2
1.60.0
1.61.0rc1
1.61.0
1.61.1
1.62.0rc1
1.62.0rc2
1.62.0rc3
1.62.0
1.63.0rc1
1.63.0
1.63.1
1.64.0rc1
1.64.0rc2
1.64.0
1.65.0rc1
1.65.0rc2
1.65.0
1.66.0rc1
1.66.0rc2
1.66.0
1.67.0rc1
1.67.0
1.68.0rc1
1.68.0rc2
1.68.0
1.69.0rc1
1.69.0rc2
1.69.0rc4
1.69.0
1.70.0rc1
1.70.0rc2
1.70.0
1.70.1
1.71.0rc1
1.71.0rc2
1.71.0
1.72.0rc1
1.72.0
1.73.0rc2
1.73.0
1.74.0rc1