CVE-2026-63097

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 v3 4.3 MEDIUM

4.3^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/geo-chen/oss/blob/main/dendrite.md#finding-3-context-returns-current-room-state-to-non-members-and-left-users-history-visibility-bypass
https://www.vulncheck.com/advisories/dendrite-syncapi-context-endpoint-post-leave-state-exposure

Configurations

No configuration.

History

17 Jul 2026, 16:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-07-17 16:17

Updated : 2026-07-23 20:17

NVD link : CVE-2026-63097

Mitre link : CVE-2026-63097

CVE.ORG link : CVE-2026-63097

JSON object : View

Products Affected

No product.

CWE

CWE-863

Incorrect Authorization

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