CVE-2023-43796

Synapse is an open-source Matrix homeserver Prior to versions 1.95.1 and 1.96.0rc1, cached device information of remote users can be queried from Synapse. This can be used to enumerate the remote users known to a homeserver. System administrators are encouraged to upgrade to Synapse 1.95.1 or 1.96.0rc1 to receive a patch. As a workaround, the federation_domain_whitelist can be used to limit federation traffic with a homeserver.

Impact

Cached device information of remote users can be queried from Synapse. This can be used to enumerate the remote users known to a homeserver.

Patches

System administrators are encouraged to upgrade to Synapse 1.95.1 as soon as possible.

Workarounds

The federation_domain_whitelist can be used to limit federation traffic with a homeserver.

Synapse is an open-source Matrix homeserver Prior to versions 1.95.1 and 1.96.0rc1, cached device information of remote users can be queried from Synapse. This can be used to enumerate the remote users known to a homeserver. System administrators are encouraged to upgrade to Synapse 1.95.1 or 1.96.0rc1 to receive a patch. As a workaround, the federation_domain_whitelist can be used to limit federation traffic with a homeserver.

Synapse is an open-source Matrix homeserver Prior to versions 1.95.1 and 1.96.0rc1, cached device information of remote users can be queried from Synapse. This can be used to enumerate the remote users known to a homeserver. System administrators are encouraged to upgrade to Synapse 1.95.1 or 1.96.0rc1 to receive a patch. As a workaround, the federation_domain_whitelist can be used to limit federation traffic with a homeserver.

These are all security issues fixed in the matrix-synapse-1.95.1-1.1 package on the GA media of openSUSE Tumbleweed.

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)