CVE-2022-39246 is a high-severity (CVSS 7.5) Improper Authentication vulnerability in org.matrix.android:matrix-android-sdk2. A fix is available for org.matrix.android:matrix-android-sdk2 — see the affected versions and patch details below.
matrix-android-sdk2 vulnerable to impersonation via forwarded Megolm sessions
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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-2022-39246.
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-2022-39246 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 377,636 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
org.matrix.android:matrix-android-sdk2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Impact
An attacker cooperating with a malicious homeserver can construct messages appearing to have come from another person. Such messages will be marked with a grey shield on some platforms, but this may be missing in others.
This attack is possible due to the matrix-android-sdk2 implementing a too permissive key forwarding strategy on the receiving end.
Key forwarding is a mechanism allowing clients to recover from “unable to decrypt” messages when they missed the initial key distribution, at the time the message was originally sent. Examples include accessing message history before they joined the room but also when some network/federation errors have occurred.
Patches
The default policy for accepting key forwards has been made more strict in the matrix-android-sdk2. The matrix-android-sdk2 will now only accept forwarded keys in response to previously issued requests and only from own, verified devices.
A unique exception to this rule is with the experimental MSC3061, that is forwarding room keys for past messages when invited in a room configured with the proper history visibility setting. Such key forwards are parked upon receipt and are only accepted if the SDK receives an invitation for that room from the inviter in a limited time window.
The SDK now sets a trusted flag on the decrypted message upon decryption, based on whether the key used to decrypt the message was received from a trusted source. Clients need to ensure that messages decrypted with a key with trusted = false are decorated appropriately (for example, by showing a warning for such messages).
Workarounds
Current users of the SDK can disable key forwarding in their forks using CryptoService#enableKeyGossiping(enable: Boolean).
References
For more information
If you have any questions or comments about this advisory, e-mail us at [email protected].
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.matrix.android:matrix-android-sdk2 | all versions | 1.5.1org.matrix.android:matrix-android-sdk2:1.5.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.matrix.android:matrix-android-sdk2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.matrix.android:matrix-android-sdk2 to 1.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-39246 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-2022-39246 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2022-39246. 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-2022-39246 in your dependencies?
O3 Security finds CVE-2022-39246 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.