CVE-2026-63097: Incorrect Authorization in matrix-org dendrite
Dendrite through 0.13.8 contains an improper access control vulnerability in the syncapi /context endpoint (syncapi/routing/context.go) that allows authenticated local users to access post-leave room state events by exploiting a flawed membership check that evaluates only the RoomExists field while ignoring IsInRoom, HasBeenInRoom, and Membership fields. Attackers who have left a room can call the rooms context API endpoint for a previously permitted event and receive unfiltered current room state that the /messages and /sync endpoints correctly withhold.
AI Analysis
Technical Summary
CVE-2026-63097 describes an improper authorization vulnerability in matrix-org's Dendrite through version 0.13.8. The issue resides in the syncapi /context endpoint (syncapi/routing/context.go), where the membership check only evaluates the RoomExists field and neglects IsInRoom, HasBeenInRoom, and Membership fields. As a result, authenticated local users who have left a room can still retrieve unfiltered current room state events by calling the rooms context API endpoint. This bypasses the intended access controls that the /messages and /sync endpoints enforce.
Potential Impact
The vulnerability allows authenticated users who have left a room to access current room state events that should be restricted. This could lead to unauthorized disclosure of room state information that is normally withheld from users no longer in the room. There is no indication of privilege escalation or remote unauthenticated exploitation. The CVSS 4.0 base score is 5.3 (medium severity), reflecting network attack vector with low complexity and low impact on confidentiality.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary mitigation is currently documented. Until a patch is available, restrict access to authenticated users carefully and monitor for updates from matrix-org regarding a fix.
CVE-2026-63097: Incorrect Authorization in matrix-org dendrite
Description
Dendrite through 0.13.8 contains an improper access control vulnerability in the syncapi /context endpoint (syncapi/routing/context.go) that allows authenticated local users to access post-leave room state events by exploiting a flawed membership check that evaluates only the RoomExists field while ignoring IsInRoom, HasBeenInRoom, and Membership fields. Attackers who have left a room can call the rooms context API endpoint for a previously permitted event and receive unfiltered current room state that the /messages and /sync endpoints correctly withhold.
CVSS v4.0
Score 5.3medium
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-63097 describes an improper authorization vulnerability in matrix-org's Dendrite through version 0.13.8. The issue resides in the syncapi /context endpoint (syncapi/routing/context.go), where the membership check only evaluates the RoomExists field and neglects IsInRoom, HasBeenInRoom, and Membership fields. As a result, authenticated local users who have left a room can still retrieve unfiltered current room state events by calling the rooms context API endpoint. This bypasses the intended access controls that the /messages and /sync endpoints enforce.
Potential Impact
The vulnerability allows authenticated users who have left a room to access current room state events that should be restricted. This could lead to unauthorized disclosure of room state information that is normally withheld from users no longer in the room. There is no indication of privilege escalation or remote unauthenticated exploitation. The CVSS 4.0 base score is 5.3 (medium severity), reflecting network attack vector with low complexity and low impact on confidentiality.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary mitigation is currently documented. Until a patch is available, restrict access to authenticated users carefully and monitor for updates from matrix-org regarding a fix.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-07-15T15:45:44.601Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a5b5ec82d1edb114c7fbe1d
Added to database: 07/18/2026, 11:08:56 UTC
Last enriched: 08/02/2026, 21:02:16 UTC
Last updated: 08/31/2026, 22:52:12 UTC
Views: 76
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