CVE-2021-21392

Open redirect via transitional IPv6 addresses on dual-stack networks

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.

Category

6.3
CVSS
Severity: Medium
CVSS 3.1 •
CVSS 2.0 •
EPSS 0.20%
Vendor Advisory fedoraproject.org
Affected: matrix-org synapse
Published at:
Updated at:

References

Link Tags
https://pypi.org/project/matrix-synapse/ third party advisory product
https://github.com/matrix-org/synapse/security/advisories/GHSA-5wrh-4jwv-5w78 third party advisory patch
https://github.com/matrix-org/synapse/pull/9240 third party advisory patch
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/ vendor advisory

Frequently Asked Questions

What is the severity of CVE-2021-21392?
CVE-2021-21392 has been scored as a medium severity vulnerability.
How to fix CVE-2021-21392?
To fix CVE-2021-21392, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2021-21392 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2021-21392 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2021-21392?
CVE-2021-21392 affects matrix-org synapse.
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