Description
Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Prior to version 1.94.0, a malicious server ACL event can impact performance temporarily or permanently leading to a persistent denial of service. Homeservers running on a closed federation (which presumably do not need to use server ACLs) are not affected. Server administrators are advised to upgrade to Synapse 1.94.0 or later. As a workaround, rooms with malicious server ACL events can be purged and blocked using the admin API.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| matrix-org | synapse | < 1.94.0 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | matrix-synapse | No fix yet | — |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | matrix-synapse | No fix yet | — |
| Ubuntu Pro 18.04 LTS | matrix-synapse | No fix yet | — |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | matrix-synapse | 1.94.0-2.1 | openSUSE-SU-2024:13320-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | synapse | 1.94.0-r0 | — |
| Alpine v3.23 | synapse | 1.94.0-r0 | — |
| Alpine v3.22 | synapse | 1.94.0-r0 | — |
| Alpine v3.21 | synapse | 1.94.0-r0 | — |
| Alpine v3.20 | synapse | 1.94.0-r0 | — |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | synapse | 1.94.0-r0 | — |
| Alpine v3.18 | synapse | 1.94.0-r0 | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | matrix-synapse | < 1.94.0 | 1.94.0 | GHSA-5chr-wjw5-3gq4 |
Advisories 1
- openSUSE-SU-2024:13320-1 matrix-synapse-1.94.0-2.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
References
- https://github.com/matrix-org/synapse/security/advisories/GHSA-5chr-wjw5-3gq4
- https://github.com/matrix-org/synapse/pull/16360
- https://matrix-org.github.io/synapse/latest/admin_api/rooms.html#version-2-new-version
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WRO4MPQ6HOXIUZM6RJP6VTCTMV7RD2T3/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/KEVRB4MG5UXQ5RLZHSUJXM5GWEBYYS5B/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/N6P4QULVUE254WI7XF2LWWOGHCYVFXFY/
- https://security.gentoo.org/glsa/202401-12