// For flags

CVE-2023-42453

Improper validation of receipts allows forged read receipts in matrix synapse

Severity Score

4.3
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

Track
*SSVC
Descriptions

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.

Synapse es un servidor doméstico Matrix de código abierto escrito y mantenido por la Fundación Matrix.org. Los usuarios podían falsificar recibos de lectura para cualquier evento (si conocían el ID de la sala y el ID del evento). Tenga en cuenta que los usuarios no pudieron ver los eventos, simplemente marcarlos como leídos. Esto podría resultar confuso ya que los clientes mostrarán el evento tal como lo leyó el usuario, incluso si no están en la sala. Este problema se solucionó en la versión 1.93.0. Se recomienda a los usuarios que actualicen. No se conocen workarounds para este problema.

It was discovered that Synapse network policies could be bypassed via specially crafted URLs. An attacker could possibly use this issue to bypass authentication mechanisms. It was discovered that Synapse exposed cached device information. An attacker could possibly use this issue to gain access to sensitive information. It was discovered that Synapse could be tricked into rejecting state changes in rooms. An attacker could possibly use this issue to cause Synapse to stop functioning properly, resulting in a denial of service. This issue was only fixed in Ubuntu 20.04 LTS and Ubuntu 22.04 LTS.

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None
Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None
Attack Vector
Network
Attack Complexity
Low
Authentication
Single
Confidentiality
None
Integrity
Partial
Availability
None
* Common Vulnerability Scoring System
SSVC
  • Decision:Track
Exploitation
None
Automatable
No
Tech. Impact
Partial
* Organization's Worst-case Scenario
Timeline
  • 2023-09-08 CVE Reserved
  • 2023-09-26 CVE Published
  • 2025-05-14 EPSS Updated
  • 2025-06-18 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-285: Improper Authorization
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Matrix
Search vendor "Matrix"
 Synapse
Search vendor "Matrix" for product "Synapse"
 >= 1.34.0 < 1.93.0
Search vendor "Matrix" for product "Synapse" and version " >= 1.34.0 < 1.93.0"
-
Affected
Fedoraproject
Search vendor "Fedoraproject"
 Fedora
Search vendor "Fedoraproject" for product "Fedora"
 37
Search vendor "Fedoraproject" for product "Fedora" and version "37"
-
Affected
Fedoraproject
Search vendor "Fedoraproject"
 Fedora
Search vendor "Fedoraproject" for product "Fedora"
 38
Search vendor "Fedoraproject" for product "Fedora" and version "38"
-
Affected