Vulnerability CVE-2021-41281


Published: 2021-11-23

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.

Type:

CWE-22

(Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'))

CVSS2 => (AV:N/AC:M/Au:N/C:N/I:P/A:N)

CVSS Base Score
Impact Subscore
Exploitability Subscore
4.3/10
2.9/10
8.6/10
Exploit range
Attack complexity
Authentication
Remote
Medium
No required
Confidentiality impact
Integrity impact
Availability impact
None
Partial
None
Affected software
Matrix -> Synapse 

 References:
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

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