GHSA-pfw4-xjgm-267c
HIGHDendrite signature checks not applied to some retrieved missing events
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.
Blast Radius
github.com/matrix-org/dendriteReal-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
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.
Patches
The problem has been fixed in Dendrite 0.9.8.
Workarounds
There are no workarounds.
Special thanks
Tulir Asokan, who spotted the issue originally.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/matrix-org/dendrite | all versions | 0.9.8 |
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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/matrix-org/dendrite to 0.9.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-pfw4-xjgm-267c 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 pinpoints whether GHSA-pfw4-xjgm-267c is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-pfw4-xjgm-267c. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-pfw4-xjgm-267c in your dependencies?
O3 detects GHSA-pfw4-xjgm-267c across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.