CVE-2026-63097
Dendrite 0.13.8 syncapi /context Endpoint Post-Leave State Exposure
- State
- Published
- Severity
- 5.3 Medium
- Published
- Jul 17, 2026
- Updated
- Jul 28, 2026
- Reserved
- Jul 15, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 5.3 Medium | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 4.3 Medium | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N | VulnCheck |
Weaknesses
- CWE-863 Incorrect Authorization
Affected Products
| Product | Versions |
|---|---|
dendritematrix-org |
|
References
- Researcher Disclosuretechnical-descriptionexploit
- https://www.vulncheck.com/advisories/dendrite-syncapi-context-endpoint-post-leave-state-exposurethird-party-advisory
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