CVE-2022-36009 is a medium-severity (CVSS 5) CWE-863 vulnerability in github.com/matrix-org/dendrite. A fix is available for github.com/matrix-org/dendrite — see the affected versions and patch details below.
Incorrect parsing of access level in gomatrixserverlib and dendrite
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2022-36009.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2022-36009 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,238 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/matrix-org/dendrite🐹github.com/matrix-org/gomatrixserverlibReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
gomatrixserverlib is a Go library for matrix protocol federation. Dendrite is a Matrix homeserver written in Go, an alternative to Synapse. The power level parsing within gomatrixserverlib was failing to parse the "events_default" key of the m.room.power_levels event, defaulting the event default power level to zero in all cases. Power levels are the matrix terminology for user access level. In rooms where the "events_default" power level had been changed, this could result in events either being incorrectly authorised or rejected by Dendrite servers. gomatrixserverlib contains a fix as of commit 723fd49 and Dendrite 0.9.3 has been updated accordingly. Matrix rooms where the "events_default" power level has not been changed from the default of zero are not vulnerable. Users are advised to upgrade. There are no known workarounds for this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/matrix-org/dendrite | all versions | 0.9.3go get github.com/matrix-org/dendrite@v0.9.3 |
| 🐹Go | github.com/matrix-org/gomatrixserverlib | all versions | 0.0.0-20220815091947-723fd495dde8go get github.com/matrix-org/gomatrixserverlib@v0.0.0-20220815091947-723fd495dde8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/matrix-org/dendrite, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/matrix-org/dendrite to 0.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-36009 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2022-36009 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2022-36009. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2022-36009 in your dependencies?
O3 Security finds CVE-2022-36009 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.