GHSA-4jf8-g8wp-cx7c
Matrix JavaScript SDK's key history sharing could share keys to malicious devices
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
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
matrix-js-sdknpmDescription
Impact
In matrix-js-sdk versions 9.11.0 through 34.7.0, the method MatrixClient.sendSharedHistoryKeys is vulnerable to interception by malicious homeservers. The method implements functionality proposed in MSC3061 and can be used by clients to share historical message keys with newly invited users, granting them access to past messages in the room.
However, it unconditionally sends these "shared" keys to all of the invited user's devices, regardless of whether the user's cryptographic identity is verified or whether the user's devices are signed by that identity. This allows the attacker to potentially inject its own devices to receive sensitive historical keys without proper security checks.
Note that this only affects clients running the SDK with the legacy crypto stack. Clients using the new Rust cryptography stack (i.e. those that call MatrixClient.initRustCrypto() instead of MatrixClient.initCrypto()) are unaffected by this vulnerability, because MatrixClient.sendSharedHistoryKeys() raises an exception in such environments.
Patches
Fixed in matrix-js-sdk 34.8.0 by removing the vulnerable functionality.
Workarounds
Remove use of affected functionality from clients.
References
For more information
If you have any questions or comments about this advisory, please email us at security at matrix.org.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | matrix-js-sdk | ≥ 9.11.0&&< 34.8.0 | 34.8.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for matrix-js-sdk. 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 matrix-js-sdk to 34.8.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4jf8-g8wp-cx7c 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-4jf8-g8wp-cx7c 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-4jf8-g8wp-cx7c. 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-4jf8-g8wp-cx7c in your dependencies?
O3 detects GHSA-4jf8-g8wp-cx7c across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.