Information disclosure in IBM AIX

1) User enumeration

EUVDB-ID: #VU14440

Risk: Medium

CVSSv3.1: 5.4 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N/E:F/RL:O/RC:C]

CVE-ID: CVE-2018-15473

CWE-ID: CWE-388 - Error Handling

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to enumerate all accounts on the system.

The vulnerability exists due to a logical error in auth2-gss.c, auth2-hostbased.c, and auth2-pubkey.c files when processing authentication requests. A remote attacker can send a specially crafted chain of packets and monitor behavior of openssh server to determine presence of a valid username. The server will drop connection upon receiving a malformed authentication packets if the username is valid.

Mitigation

Install update from vendor's website.

Vulnerable software versions

IBM AIX: 5.3 - 7.2

External links

http://aix.software.ibm.com/aix/efixes/security/openssh_advisory12.asc

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, a fully functional exploit for this vulnerability is available.