Summary
Dendrite signature checks not applied to some retrieved missing events
Workarounds
There are no workarounds.
Special thanks
Tulir Asokan, who spotted the issue originally.
Impact
Events retrieved from a remote homeserver using /get_missing_events did not have their signatures verified correctly. This could potentially allow a remote homeserver to provide invalid/modified events to Dendrite via this endpoint.
Note that this does not apply to events retrieved through other endpoints (e.g. /event, /state) as they have been correctly verified.
Homeservers that have federation disabled are not vulnerable.
CVE-2022-39200 has a CVSS score of 7.3 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.9.8); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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The problem has been fixed in Dendrite 0.9.8.
Frequently Asked Questions
- What is CVE-2022-39200? CVE-2022-39200 is a high-severity security vulnerability in github.com/matrix-org/dendrite (go), affecting versions < 0.9.8. It is fixed in 0.9.8.
- How severe is CVE-2022-39200? CVE-2022-39200 has a CVSS score of 7.3 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/matrix-org/dendrite are affected by CVE-2022-39200? github.com/matrix-org/dendrite (go) versions < 0.9.8 is affected.
- Is there a fix for CVE-2022-39200? Yes. CVE-2022-39200 is fixed in 0.9.8. Upgrade to this version or later.
- Is CVE-2022-39200 exploitable, and should I be worried? Whether CVE-2022-39200 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2022-39200 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2022-39200? Upgrade
github.com/matrix-org/dendriteto 0.9.8 or later.