CVE-2026-45056

Matrix Rust SDK: Sender-binding gaps in to-device and room-key attribution

MEDIUM
6.9
CVSS Score
Published: September 11, 2026 at 09:13 PM UTC
Updated: September 30, 2026 at 07:57 PM UTC
1 product affected across 1 vendorMatrix Rust SDK

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Severity
MEDIUM6.9
Exploit prediction
EPSS 0.3%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 0.16.1
Affected range stops below 0.16.1, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.9MEDIUMGitHub_M
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-290

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