Vulnerabilities
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CVE Vulnerabilities

CVE-2018-20217

Reachable Assertion

Published: Dec 26, 2018 | Modified: Nov 21, 2024
CVSS 3.x
5.3
MEDIUM
Source:
NVD
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
CVSS 2.x
3.5 LOW
AV:N/AC:M/Au:S/C:N/I:N/A:P
RedHat/V2
RedHat/V3
5.3 MODERATE
CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Ubuntu
MEDIUM
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Additional information
NVDhttps://nvd.nist.gov/vuln/detail/CVE-2018-20217
CWEhttps://cwe.mitre.org/data/definitions/617.html

A Reachable Assertion issue was discovered in the KDC in MIT Kerberos 5 (aka krb5) before 1.17. If an attacker can obtain a krbtgt ticket using an older encryption type (single-DES, triple-DES, or RC4), the attacker can crash the KDC by making an S4U2Self request.

Weakness

The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.

Affected Software

NameVendorStart VersionEnd Version
KerberosMit*5-1.17 (excluding)
Red Hat Ansible Tower 3.4 for RHEL 7RedHatansible-tower-34/ansible-tower-memcached:1.4.15-28*
Red Hat Ansible Tower 3.4 for RHEL 7RedHatansible-tower-35/ansible-tower-memcached:1.4.15-28*
Red Hat Ansible Tower 3.4 for RHEL 7RedHatansible-tower-37/ansible-tower-memcached-rhel7:1.4.15-28*
Red Hat Enterprise Linux 7RedHatkrb5-0:1.15.1-37.el7_7.2*
Krb5Ubuntubionic*
Krb5Ubuntucosmic*
Krb5Ubuntudisco*
Krb5Ubuntueoan*
Krb5Ubuntuesm-infra-legacy/trusty*
Krb5Ubuntuesm-infra/bionic*
Krb5Ubuntuesm-infra/xenial*
Krb5Ubuntuprecise/esm*
Krb5Ubuntutrusty*
Krb5Ubuntutrusty/esm*
Krb5Ubuntuupstream*
Krb5Ubuntuxenial*

Extended Description

While assertion is good for catching logic errors and reducing the chances of reaching more serious vulnerability conditions, it can still lead to a denial of service. For example, if a server handles multiple simultaneous connections, and an assert() occurs in one single connection that causes all other connections to be dropped, this is a reachable assertion that leads to a denial of service.

Potential Mitigations

References

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