CVE-2021-21392
Description
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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2021-21392
OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| debian | forky | fixed | 1.28.0-1 |
| debian | sid | fixed | 1.28.0-1 |
Package impact
| Ecosystem | Package | Vulnerable | Fixed |
|---|---|---|---|
| PyPI | matrix-synapse | <1.28.0rc1 | 1.28.0rc1 |
| PyPI | matrix-synapse | <1.28.0 | 1.28.0 |
References
- https://github.com/matrix-org/synapse/security/advisories/GHSA-5wrh-4jwv-5w78
- https://nvd.nist.gov/vuln/detail/CVE-2021-21392
- https://github.com/matrix-org/synapse/pull/9240
- https://github.com/matrix-org/synapse/commit/4ca054a4eaa714d0befb4fc30b19a1131e52c9cc
- https://github.com/matrix-org/synapse
- https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2021-25.yaml
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY
- https://pypi.org/project/matrix-synapse
- https://pypi.org/project/matrix-synapse/
- https://security-tracker.debian.org/tracker/CVE-2021-21392
Verify integrity in audit chain (admin only). AS-IS.