CVE-2026-45056
Fix: matrix-org/matrix-rust-sdk#6553CVE-2026-45056 is a security vulnerability in matrix-sdk-crypto. O3 Security confirms whether CVE-2026-45056 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Matrix Rust SDK: Sender-binding gaps in to-device and room-key attribution
Real-World Exposure
matrix-sdk-cryptoReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Impact
The matrix-sdk-crypto crate before 0.16.1 is missing a check for the sender's user ID when decrypting an Olm-encrypted to-device message containing the sender_device_keys property.
This could be exploited to spoof the sender of an encrypted to-device message, but only if the attacker colludes with (or is) the homeserver operator.
Patches
This issue is fixed in matrix-sdk-crypto 0.16.1.
Workarounds
There are no known workarounds for the issue.
References
This issue was fixed in https://github.com/matrix-org/matrix-rust-sdk/pull/6553.
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 |
|---|---|---|---|
| 🦀crates.io | matrix-sdk-crypto | ≥ 0.12.0&&< 0.16.1 | 0.16.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for matrix-sdk-crypto. 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-sdk-crypto to 0.16.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45056 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 CVE-2026-45056 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 CVE-2026-45056. 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-2026-45056 in your dependencies?
O3 detects CVE-2026-45056 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.