Quick answers
- Is CVE-2026-63097 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-63097 being exploited in the wild.
- How severe is CVE-2026-63097?
- Medium severity, with a CVSS score of 4.3, published 17 July 2026.
- Which products and versions are affected?
- Matrix.org Dendrite <= 0.13.8.
- Is there a fix for CVE-2026-63097?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-63097 attacked?
- It is attacked over the network, in a hosted service.
- Am I affected by CVE-2026-63097?
- Check whether you run Matrix.org Dendrite at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
An improper access control vulnerability exists in the syncapi /context endpoint (syncapi/routing/context.go) of Dendrite. The vulnerability stems from a flawed membership check that only evaluates the RoomExists field while failing to verify IsInRoom, HasBeenInRoom, or Membership status. An authenticated attacker who has previously left a room can call the context API for an event they were originally permitted to see; the server then returns the unfiltered current room state. This bypasses the history visibility restrictions correctly enforced by the /messages and /sync endpoints. The product repository was archived in November 2024, and no official patch is currently noted.
Affected products
- Matrix.org Dendrite <= 0.13.8
Timeline
- 2024-11-25: other: Repository archived by owner
- 2026-07-17: disclosed: Vulnerability published and CVE assigned