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

  - Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference "homeserver"
    implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a
    room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or
    `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will
    not be correctly sent to other servers over federation. This affects any server which accepts federation
    requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the
    implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround
    homeserver administrators could limit access to the federation API to trusted servers (for example via
    `federation_domain_whitelist`). (CVE-2020-26257)

Upstream release notes:
https://github.com/matrix-org/synapse/blob/master/CHANGES.md#synapse-1 240rc1-2020-12-02 This release includes some minor changes which may affect homeserver admins:
https://github.com/matrix-org/synapse/blob/develop/UPGRADE.rst#upgradi ng-to-v1240

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website.
Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

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

  - Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference homeserver     implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a     room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or     `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will     not be correctly sent to other servers over federation. This affects any server which accepts federation     requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the     implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround     homeserver administrators could limit access to the federation API to trusted servers (for example via     `federation_domain_whitelist`). (CVE-2020-26257)

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

Matrix developers reports :

A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a /send_join, /send_leave, /invite or /exchange_third_party_invite request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers.

ID	Name	Product	Family	Published	Updated	Severity
416034	SCA: security update for matrix-synapse (GHSA-hxmp-pqch-c8mm)	Tenable Self-Hosted Container Security	SCA Checks	1/23/2025	7/2/2026	high
407300	Alpine: multiple synapse packages: security update to 1.24.0-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	10/31/2023	7/2/2026	high
416034	SCA: security update for matrix-synapse (GHSA-hxmp-pqch-c8mm)	Tenable Cloud Security	SCA Checks	1/23/2025	7/2/2026	high
407300	Alpine: multiple synapse packages: security update to 1.24.0-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	10/31/2023	7/2/2026	high
144475	Fedora 32 : matrix-synapse (2020-a2172c484d)	Nessus	Fedora Local Security Checks	12/21/2020	2/1/2024	medium
257035	Linux Distros Unpatched Vulnerability : CVE-2020-26257	Nessus	Misc.	8/27/2025	7/12/2026	medium
144167	FreeBSD : py-matrix-synapse -- DoS on Federation API (cfa0be42-3cd7-11eb-9de7-641c67a117d8)	Nessus	FreeBSD Local Security Checks	12/14/2020	2/2/2024	medium
144480	Fedora 33 : matrix-synapse (2020-eeb66c2ece)	Nessus	Fedora Local Security Checks	12/21/2020	2/1/2024	medium

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