CVE-2026-63097 | Dendrite through 0.13.8 contains an improper access control … | CVSS 4.3 MEDIUM

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.

Metadata

CVE ID: CVE-2026-63097
State: PUBLISHED
Assigner: VulnCheck
Reserved: 2026-07-15 15:45 UTC
Published: 2026-07-17 15:32 UTC
Last updated: 2026-07-17 15:32 UTC
Primary CWE: CWE-863
Incorrect Authorization
Vendor / Product: matrix-org / dendrite
Sources: cve.org · NVD

Severity & Metrics

4.3 MEDIUM CVSS 3.1

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Affected products (1)

Vendor	Product	Platform	Versions
matrix-org	dendrite	—	0 ≤ 0.13.8

Weakness (CWE)

CWE	Source	Description
CWE-863	cna	Incorrect Authorization

CVSS scores (2)

Score	Severity	Version	Source	Vector
5.3	MEDIUM	4.0	cna	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
4.3	MEDIUM	3.1	cna	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

References (2)