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Ubuntu Security Notice USN-7444-1
April 22, 2025

matrix-synapse vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in Synapse.

Software Description:
- matrix-synapse: Synapse: Matrix homeserver written in Python/Twisted.

Details:

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. (CVE-2023-32683)

It was discovered that Synapse exposed cached device information. An
attacker could possibly use this issue to gain access to sensitive
information. (CVE-2023-43796)

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.
(CVE-2022-39374)

It was discovered that Synapse stored user credentials in a server's
database temporarily. An attacker could possibly use this issue to
gain access to sensitive information. This issue was only fixed in
Ubuntu 22.04 LTS. (CVE-2023-41335)

It was discovered that Synapse could incorrectly respond to server
authorization events. An attacker could possibly use this issue to
bypass authentication mechanisms. This issue was only fixed in Ubuntu
22.04 LTS. (CVE-2022-39335)

It was discovered that Synapse could be manipulated to mark messages
as read when they had not been viewed. An attacker could possibly use
this issue to perform repudiation-based attacks. This issue was only
fixed in Ubuntu 22.04 LTS. (CVE-2023-42453)

It was discovered that Synapse had several memory-related issues. An
attacker could possibly use this issue to cause Synapse to crash,
resulting in a denial of service. This issue was only fixed in Ubuntu
22.04 LTS. (CVE-2024-31208)

It was discovered that Synapse could run external tools due to a
unchecked thumbnail rendering routine. An attacker could possibly use
this issue to cause Synapse to crash, resulting in a denial of service,
or execute arbitrary code. This issue was only fixed in Ubuntu
22.04 LTS. (CVE-2024-53863)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 22.04 LTS
  matrix-synapse                  1.53.0-1ubuntu0.1~esm2
                                  Available with Ubuntu Pro

Ubuntu 20.04 LTS
  matrix-synapse                  1.11.0-1ubuntu0.1~esm2
                                  Available with Ubuntu Pro

Ubuntu 18.04 LTS
  matrix-synapse                  0.24.0+dfsg-1ubuntu0.1~esm4
                                  Available with Ubuntu Pro

After a standard system update you need to restart Synapse to make
all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-7444-1
  CVE-2022-39335, CVE-2022-39374, CVE-2023-32683, CVE-2023-41335,
  CVE-2023-42453, CVE-2023-43796, CVE-2024-31208, CVE-2024-53863