CVE catalog
CVE-2021-21392
UBUNTU-CVE-2021-21392
- Severity
- Medium · CVSS 6.3
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:N - Published
- Updated
- Source
- [NVD] · [CVE record]
- EPSS
- 0.94% · Oct 27, 2026
Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.28.0 requests to user provided domains were not restricted to external IP addresses when transitional IPv6 addresses were used. Outbound requests to federation, identity servers, when calculating the key validity for third-party invite events, sending push notifications, and generating URL previews are affected. This could cause Synapse to make requests to internal infrastructure on dual-stack networks. See referenced GitHub security advisory for details and workarounds.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Ubuntu | matrix-synapse | pro | 0.19.2+dfsg-6 | vulnerable |
| Ubuntu | matrix-synapse | pro | 0.24.0+dfsg-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 0.24.0+dfsg-1ubuntu0.1~esm1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 0.24.0+dfsg-1ubuntu0.1~esm4 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.3.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.4.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.5.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.5.1-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.6.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.6.1-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.7.0-2 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.7.1-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.7.2-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.7.3-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.8.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.9.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.9.1-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.10.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.10.0-2 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.11.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.11.0-1ubuntu0.1~esm2 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.39.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.47.0-2 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.47.1-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.48.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.49.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.49.2-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.50.1-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.50.2-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.51.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.52.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.53.0-1 | vulnerable |
| Ubuntu | matrix-synapse | pro | 1.53.0-1ubuntu0.1~esm2 | vulnerable |
Fixed-version evidence
OpenFactory catalog packages
No matching packages in this catalog.
Observed: