Access Restriction Bypass Affecting matrix-synapse package, versions [,1.69.0rc1)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published25 May 2023
- disclosed24 May 2023
- creditUnknown
Introduced: 24 May 2023
CVE-2022-39335 (opens in a new tab)How to fix?
Upgrade matrix-synapse to version 1.69.0rc1 or higher.
Overview
matrix-synapse is an ecosystem for open federated Instant Messaging and VoIP.
Affected versions of this package are vulnerable to Access Restriction Bypass due to Synapse homeservers answering a query for authorisation events not sufficiently checking that the requesting server should be able to access them. Authorisation events include power level events (the list of user IDs and their power levels at the time) and relevant membership events (including the display name of the sender of that event), as well as events like m.room.create, m.room.third_party_invite and m.room.join_rules. Non-authorisation events are unaffected, so it isn't possible to extract message contents this way.
NOTE: This issue is only exploitable when an attacker knows the ID of a target room and the ID of an event from that room, which increases the complexity of a realistic attack. Additionally, this issue is of negligible consequence for public rooms given that any server can easily join the roomand view authorisation events. Deployments in a closed federation where all homeservers are trustworthy are not affected.