Weak pseudo-random number generator in Apereo CAS

Published: 2019-09-24

Risk	Medium
Patch available	YES
Number of vulnerabilities	1
CVE-ID	CVE-2019-10754
CWE-ID	CWE-338
Exploitation vector	Network
Public exploit	Public exploit code for vulnerability #1 is available.
Vulnerable software Subscribe	Apereo CAS Web applications / Other software
Vendor	Apereo Foundation

Security Bulletin

This security bulletin contains one medium risk vulnerability.

1) Use of cryptographically weak pseudo-random number generator (PRNG)

EUVDB-ID: #VU21291

Risk: Medium

CVSSv3.1: 5.9 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C]

CVE-ID: CVE-2019-10754

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

Exploit availability: No

Description

The vulnerability allows a remote attacker to bypass authentication.

The vulnerability exists due to the application generates tokens using a weak cryptographic algorithm provided by Apache commons-lang3 RandomStringUtils. A remote attacker can guess randomly generate tokens and bypass security restriction that rely on these tokens.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Apereo CAS: 3.0 - 6.1.0 RC4

External links

http://github.com/alex91ar/randomstringutils
http://github.com/apereo/cas/commit/40bf278e66786544411c471de5123e7a71826b9f
http://medium.com/@alex91ar/the-java-soothsayer-a-practical-application-for-insecure-randomness-c67...

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. However, proof of concept for this vulnerability is available.