RHSA-2021:3576 - Security Advisory

Topic

An update for krb5 is now available for Red Hat Enterprise Linux 8.

Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Description

Kerberos is a network authentication system, which can improve the security of your network by eliminating the insecure practice of sending passwords over the network in unencrypted form. It allows clients and servers to authenticate to each other with the help of a trusted third party, the Kerberos key distribution center (KDC).

Security Fix(es):

• krb5: Sending a request containing PA-ENCRYPTED-CHALLENGE padata element without using FAST could result in NULL dereference in KDC which leads to DoS (CVE-2021-36222)
• krb5: NULL pointer dereference in process_tgs_req() in kdc/do_tgs_req.c via a FAST inner body that lacks server field (CVE-2021-37750)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the updated packages, running Kerberos services (krb5kdc, kadmin, and kprop) will be restarted automatically.

Affected Products

• Red Hat Enterprise Linux for x86_64 8 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 8.4 x86_64
• Red Hat Enterprise Linux Server - AUS 8.4 x86_64
• Red Hat Enterprise Linux for IBM z Systems 8 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 8.4 s390x
• Red Hat Enterprise Linux for Power, little endian 8 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 8.4 ppc64le
• Red Hat Enterprise Linux Server - TUS 8.4 x86_64
• Red Hat Enterprise Linux for ARM 64 8 aarch64
• Red Hat Enterprise Linux for ARM 64 - Extended Update Support 8.4 aarch64
• Red Hat Enterprise Linux Server (for IBM Power LE) - Update Services for SAP Solutions 8.4 ppc64le
• Red Hat Enterprise Linux Server - Update Services for SAP Solutions 8.4 x86_64

Fixes

• BZ - 1983720 - CVE-2021-36222 krb5: Sending a request containing PA-ENCRYPTED-CHALLENGE padata element without using FAST could result in NULL dereference in KDC which leads to DoS
• BZ - 1996834 - CVE-2021-37750 krb5: NULL pointer dereference in process_tgs_req() in kdc/do_tgs_req.c via a FAST inner body that lacks server field

CVEs

• CVE-2021-36222
• CVE-2021-37750

References

• https://access.redhat.com/security/updates/classification/#moderate