#VU76258 Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) in Synapse and Sydent - CVE-2019-11842

Vulnerability identifier: #VU76258

Vulnerability risk: Medium

CVSSv4.0: 2.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2019-11842

CWE-ID: CWE-338

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Synapse
Server applications / Conferencing, Collaboration and VoIP solutions
Sydent
Server applications / Directory software, identity management

Vendor: Matrix.org

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

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External links
https://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/

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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.