Weak pseudo-random number generator in Matrix Sydent and Synapse

1) Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

EUVDB-ID: #VU76258

Risk: Medium

CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2019-11842

CWE-ID: CWE-338 - Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

Exploit availability: No

Description

The vulnerability allows a remote attacker to gain unauthorized access to the application.

The vulnerability exists due to usage of a weak algorithm to generate a Sydent authentication token or a Synapse random ID. A remote attacker can brute-force the token and gain unauthorized access to the application.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Synapse: before 0.99.3.1

Sydent: before 1.0.3

External links

http://matrix.org/blog/2019/05/03/security-updates-sydent-1-0-3-synapse-0-99-3-1-and-riot-android-0-9-0-0-8-99-0-8-28-a/

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.