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Security Bulletin: Vulnerability in MIT Kerberos 5 affects PowerSC (CVE-2021-37750)

Security Bulletin


Summary

There is a vulnerability in MIT Kerberos 5 that affects PowerSC (CVE-2021-37750).

Vulnerability Details

CVEID:   CVE-2021-37750
DESCRIPTION:   MIT Kerberos 5 (aka krb5) is vulnerable to a denial of service, caused by a NULL pointer dereference flaw in kdc/do_tgs_req.c in the Key Distribution Center (KDC). By sending a specially-crafted FAST TGS request with no server field, a remote authenticated attacker could exploit this vulnerability to cause a denial of service condition.
CVSS Base score: 6.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/208020 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)

Affected Products and Versions

Affected Product(s) Version(s)
PowerSC 1.3
PowerSC 2.0
PowerSC 2.1

The vulnerabilities in the following filesets are being addressed:

Fileset Lower Level Upper Level
powerscStd.tnc_pm 1.3.0.4 2.1.0.2
krb5-libs-1.18.5-1.aix7.1.ppc.rpm 1.18.0 1.18.4

Note:  To find out whether the affected PowerSC filesets are installed on your systems, refer to the lslpp command found in AIX user's guide. To find out whether the affected krb5 filesets are installed on your systems, refer to the rpm command found in AIX user's guide.
Example:  lslpp -l | grep powerscStd
Example:  rpm -qa | grep krb5

Remediation/Fixes

A. FIXES
Fixes are available.
The fixes can be downloaded via ftp or http from:
The link above is to a tar file containing this signed advisory, open source fix packages, and OpenSSL signatures for each package.
         
To extract the fixes from the tar file:
tar xvf krb5_fix.tar 
cd krb5_fix
Verify you have retrieved the fixes intact:
The checksums below were generated using the "openssl dgst -sha256 [filename]" command as the following:
openssl dgst -sha256 filename
963ea0f858132a8ad1bdc898d40ec0ab028639a11707cd87511167549885c6c4 krb5-libs-1.18.5-1.aix7.1.ppc.rpm
 
These sums should match exactly. The OpenSSL signatures in the tar file and on this advisory can also be used to verify the integrity of the fixes.  If the sums or signatures cannot be confirmed, contact IBM Support.
openssl dgst -sha256 -verify [pubkey_file] -signature [advisory_file].sig [advisory_file]
openssl dgst -sha256 -verify [pubkey_file] -signature [ifix_file].sig [ifix_file]
Published advisory OpenSSL signature file location:
B. FIX AND INTERIM FIX INSTALLATION
IMPORTANT: If possible, it is recommended that a mksysb backup of the system be created. Verify it is both bootable and readable before proceeding.
To extract the fixes from the tar file:
tar xvf krb5_fix.tar
cd krb5_fix
To install a fix package:
rpm -ivh *.rpm
rpm -Uvh *.rpm
To install any dependencies along with the fix package:
yum update krb5-libs

Workarounds and Mitigations

None

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References

Complete CVSS v3 Guide
On-line Calculator v3

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Related Information

IBM Secure Engineering Web Portal
IBM Product Security Incident Response Blog

Change History

09 Sep 2022: Initial Publication

*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.

Disclaimer

Review the IBM security bulletin disclaimer and definitions regarding your responsibilities for assessing potential impact of security vulnerabilities to your environment.

Document Location

Worldwide

[{"Business Unit":{"code":"BU048","label":"Systems w\/TPS"},"Product":{"code":"SSNRQU","label":"PowerSC Express Edition"},"Component":"","Platform":[{"code":"PF002","label":"AIX"}],"Version":"1.3,2.0,2.1","Edition":""}]

Document Information

Modified date:
15 September 2022

Initial Publish date:
09 September 2022

UID

ibm16619835

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