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TI-2026-45047 Aliases CVE-2026-63097GHSA-xq7h-2f2w-f2xq

Dendrite 0.13.8 syncapi /context Endpoint Post-Leave State Exposure

Priority MEDIUM 57CWE-863Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Security bypass
Confidentiality · integrity · availability
Low · None · None
Fix status
No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-863.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00267 18th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by the CNA
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
matrix-orgdendriteup to 0.13.8—No fix listedCNA
  • dendrite Vendormatrix-org Affected up to 0.13.8 Fixed in — No fix listed CNA

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-63097
  2. 2026-10-03 Alias added: GHSA-xq7h-2f2w-f2xq

References

Exploit 1

  • TI-2023-20035 Sydent does not verify email server certificates CVSS 3.1CRITICAL 9.3
  • TI-2026-45046 Dendrite 0.13.8 SSRF via Unauthenticated Legacy Media Download Endpoint CVSS 4.0MEDIUM 6.9
  • TI-2026-45045 Dendrite 0.13.8 Improper Authorization via POST account/3pid/delete Endpoint CVSS 4.0HIGH 7.1
  • TI-2023-15617 Synapse Outgoing federation to specific hosts can be disabled by sending malicious invites CVSS 3.1MEDIUM 5.0
  • TI-2023-20039 matrix-appservice-irc IRC command injection via admin commands containing newlines CVSS 3.1CRITICAL 9.8
  • TI-2021-13807 Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while… CVSS 3.1CRITICAL 9.8
See all 115 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences