CVE-2021-41281 Information

Description

Synapse is a package for Matrix homeservers written in Python 3/Twisted. Prior to version 1.47.1 Synapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory. No authentication is required for the affected endpoint. The last 2 directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker which limits the impact. Homeservers with the media repository disabled are unaffected. Homeservers with a federation whitelist are also unaffected since Synapse will check the remote hostname including the trailing ../s against the whitelist. Server administrators should upgrade to 1.47.1 or later. Server administrators using a reverse proxy could at the expense of losing media functionality may block the certain endpoints as a workaround. Alternatively non-containerized deployments can be adapted to use the hardened systemd config.

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Reference

https://github.com/matrix-org/synapse/releases/tag/v1.47.1 https://github.com/matrix-org/synapse/security/advisories/GHSA-3hfw-x7gx-437c https://github.com/matrix-org/synapse/commit/91f2bd090 https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/N3WY56LCEZ4ZECLWV5KMAXF2PSMUB4F2/ https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/EU7QRE55U4IUEDLKT5IYPWL3UXMELFAS/

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

HIGH

Base Score

NONE

Base Severity

7.5