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 1.25.0, a malicious homeserver could redirect requests to their .well-known file to a large file. This can lead to a denial of service attack where homeservers will consume significantly more resources when requesting the .well-known file of a malicious homeserver. This affects any server which accepts federation requests from untrusted servers. Issue is resolved in version 1.25.0. As a workaround the `federation_domain_whitelist` setting can be used to restrict the homeservers communicated with over federation.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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 1.25.0, a malicious     homeserver could redirect requests to their .well-known file to a large file. This can lead to a denial of     service attack where homeservers will consume significantly more resources when requesting the .well-known     file of a malicious homeserver. This affects any server which accepts federation requests from untrusted     servers. Issue is resolved in version 1.25.0. As a workaround the `federation_domain_whitelist` setting     can be used to restrict the homeservers communicated with over federation. (CVE-2021-21274)

Note that Nessus relies on the presence of the package as reported by the vendor.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - 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 1.25.0, a malicious
    homeserver could redirect requests to their .well-known file to a large file. This can lead to a denial of
    service attack where homeservers will consume significantly more resources when requesting the .well-known
    file of a malicious homeserver. This affects any server which accepts federation requests from untrusted
    servers. Issue is resolved in version 1.25.0. As a workaround the `federation_domain_whitelist` setting
    can be used to restrict the homeservers communicated with over federation. (CVE-2021-21274)

ID	Name	Product	Family	Type	Severity
251152	Linux Distros Unpatched Vulnerability : CVE-2021-21274	Nessus	Misc.	Local	medium
408949	SCA: security update for matrix-synapse (GHSA-2hwx-mjrm-v3g8)	Tenable Cloud Security	SCA Checks	Local	medium
408949	SCA: security update for matrix-synapse (GHSA-2hwx-mjrm-v3g8)	Tenable Self-Hosted Container Security	SCA Checks	Local	medium

Detections

Analytics

CVE-2021-21274

medium

Tenable Plugins

medium

medium

medium