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Denial of service due to incorrect application of event authorization rules during state resolution

Moderate
dkasak published GHSA-p9qp-c452-f9r7 May 24, 2023

Package

pip matrix-synapse (pip)

Affected versions

>=1.62.0; <1.68.0

Patched versions

1.68.0

Description

Impact

If Synapse and a malicious homeserver are both joined to the same room, the malicious homeserver can trick Synapse into accepting previously rejected events into its view of the current state of that room. This can be exploited in a way that causes all further messages and state changes sent in that room from the vulnerable homeserver to be rejected.

Synapse homeservers are affected by this issue if and only if they are joined to rooms which members of untrusted homeservers are joined or invited to.

  • Synapse homeservers in rooms available over public federation are affected.
  • Synapse homeservers with federation disabled are not affected.
  • Synapse homeservers in a closed federation containing only trusted servers are not affected.
  • Synapse homeservers which are only joined to rooms with federation disabled1 are not affected.

Patches

Administrators of homeservers with federation enabled are advised to upgrade to 1.68.0 or higher.

Workarounds

References

For more information

If you have any questions or comments about this advisory, e-mail us at [email protected].

Footnotes

  1. See m.federate in the m.room.create definition. ↩

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVE ID

CVE-2022-39374

Weaknesses

No CWEs