1) Reachable Assertion

EUVDB-ID: #VU17350

Risk: Low

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2018-20217

CWE-ID: CWE-617 - Reachable Assertion

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a reachable assertion in in the KDC. A remote attacker can obtain a krbtgt ticket using an older encryption type (single-DES, triple-DES, or RC4) and crash the KDC by making an S4U2Self request.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Red Hat Enterprise Linux EUS Compute Node: 7.7

krb5 (Red Hat package): 1.12.2-14.el7 - 1.15.1-34.el7

Red Hat Enterprise Linux for x86_64 - Extended Update Support: 7.7

Red Hat Enterprise Linux Server for x86_64 - Update Services for SAP Solutions: 7.7

Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions: 7.7

Red Hat Enterprise Linux Server - TUS: 7.7

Red Hat Enterprise Linux for Power, little endian - Extended Update Support: 7.7

Red Hat Enterprise Linux for Power, little endian: 7

Red Hat Enterprise Linux for Power, big endian - Extended Update Support: 7.7

Red Hat Enterprise Linux for Power, big endian: 7

Red Hat Enterprise Linux for IBM z Systems - Extended Update Support: 7.7

Red Hat Enterprise Linux Server - AUS: 7.7

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_eus_compute_node:7.7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:krb5_redhat_package:1.12.2-14.el7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:krb5_redhat_package:1.13.2-10.el7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:krb5_redhat_package:1.13.2-12.el7_2:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_x86_64_-_extended_update_support:7.7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_server_-_update_services_for_sap_solutions:7.7:*:*:*:*:*:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_server_for_ibm_power_le_-_update_services_for_sap_solutions:7.7:*:*:*:*:*:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_server_-_tus:7.7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_power_little_endian_-_extended_update_support:7.7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_power_little_endian:7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_power_big_endian_-_extended_update_support:7.7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_power_big_endian:7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_ibm_z_systems_-_extended_update_support:7.7:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_server_-_aus:7.7:*:*:*:*:red_hat_enterprise_linux:*:*
• 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/RHBA-2019:2599

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.