Predictable secret key in Matrix Synapse

1) Key management errors

EUVDB-ID: #VU76259

Risk: Medium

CVSSv3.1: 6.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2019-5885

CWE-ID: CWE-320 - Key Management Errors

Exploit availability: No

Description

The vulnerability allows a remote attacker to impersonate application users.

The vulnerability exists due to usage of a weak and predictable secret key if the macaroon_secret_key authentication parameter is not set. A remote attacker can impersonate other application users.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Synapse: before 0.34.0.1

External links

http://matrix.org/blog/2019/01/15/further-details-on-critical-security-update-in-synapse-affecting-all-versions-prior-to-0-34-1-cve-2019-5885/
http://matrix.org/blog/2019/01/10/critical-security-update-synapse-0-34-0-1-synapse-0-34-1-1/
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VMCLO5PUPBA756UKY72PKUWL4RRM4W6K/
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/32Y6KD3OAHCG5P33HC2QEX3NUZOSXCGZ/

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.