CVE-2023-42453 - CVE House
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Status published Low CVE-2023-42453

Improper validation of receipts allows forged read receipts in matrix synapse

Vulnerability Description

Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Users were able to forge read receipts for any event (if they knew the room ID and event ID). Note that the users were not able to view the events, but simply mark it as read. This could be confusing as clients will show the event as read by the user, even if they are not in the room. This issue has been patched in version 1.93.0. Users are advised to upgrade. There are no known workarounds for this issue.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

No credits recorded in the NVD database.

Affected Vendor

Affected Software

synapse
Vulnerable Versions:
>= 0.34.0, < 1.93.0

Timeline

Official Publish: September 26th, 2023
Last Modified: June 18th, 2025
Added to House: July 22nd, 2026

CVSS Vectors

V3: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

Weaknesses (CWE)