CVE-2026-45056Network attack vector

Sender spoofing via unchecked embedded user ID

Published Sep 11, 2026 · Updated Sep 11, 2026

Authentication bypass in matrix-rust-sdk's matrix-sdk-crypto 0.12.0 through 0.16.0 allows remote attackers to forge to-device senders. The Olm account decryption path accepts sender_device_keys without verifying that its embedded user ID matches the event sender. Exploitation requires control of or collusion with the victim's homeserver, and the bounded consequence is false sender attribution for encrypted to-device events.

CVSS severity6.9
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in matrix-rust-sdk's matrix-sdk-crypto 0.12.0 through 0.16.0 allows remote attackers to forge to-device senders. The Olm account decryption path accepts sender_device_keys without verifying that its embedded user ID matches the event sender. Exploitation requires control of or collusion with the victim's homeserver, and the bounded consequence is false sender attribution for encrypted to-device events.

The record

CVE
CVE-2026-45056
Published
Sep 11, 2026
Updated
Sep 11, 2026
Vendor
The Matrix.org Foundation
Product
matrix-rust-sdk
Classifications
CWE-290, T1036
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Sep 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 0.12.0, < 0.16.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

The Matrix.org Foundation · matrix-rust-sdkversion=>= 0.12.0, < 0.16.1

Published CVSS scores

6.9GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-290Authentication Bypass by Spoofing
T1036Masquerading

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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