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CVE-2026-63097

4.3 · MEDIUM

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 ro…

Published Jul 17, 2026CWE-863EPSS 0.27%

Overview

CVE-2026-63097 is a medium-severity vulnerability. It was published on July 17, 2026 and has a CVSS 3.1 base score of 4.3 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 4.3, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/geo-chen/oss/blob/main/dendrite.md#finding-3-context-returns-current-room-state-to-non-members-and-left-users-history-visibility-bypassRefwww.vulncheck.com/advisories/dendrite-syncapi-context-endpoint-post-leave-state-exposure

How CyberStrike helps

Frequently asked questions

What is CVE-2026-63097?

CVE-2026-63097 is a medium-severity vulnerability. It was published on July 17, 2026 and has a CVSS 3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2026-63097?

This vulnerability has a CVSS 3.1 base score of 4.3, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-63097?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-63097?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-63097 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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