Red Hat update for openssh

1) User enumeration

EUVDB-ID: #VU14440

Risk: Medium

CVSSv4.0: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:A/U:Green]

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 updates from vendor's website.

Vulnerable software versions

Red Hat Enterprise Linux for IBM z Systems: 7

Red Hat Enterprise Linux for Scientific Computing: 7

Red Hat Enterprise Linux Desktop: 7

Red Hat Enterprise Linux Workstation: 7

Red Hat Enterprise Linux Server: 7

CPE2.3

• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_ibm_z_systems:7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_scientific_computing:7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_desktop:7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_workstation:7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_server:7:*:*:*:*:red_hat_enterprise_linux:*:*

External links

https://access.redhat.com/errata/RHSA-2019:2143

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.