Summary

There are vulnerabilities in NTPv4 that affect AIX.

Vulnerability Details

CVEID:CVE-2020-15025
**DESCRIPTION:**NTP is vulnerable to a denial of service, caused by a memory leak when a CMAC key is used and associated with a CMAC algorithm in the ntp.keys file in ntpd. By sending specially-crafted packets, a remote authenticated attacker could exploit this vulnerability to consume all available memory resources.
CVSS Base score: 4.4
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/184004 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H)

CVEID:CVE-2020-13817
**DESCRIPTION:**NTP is vulnerable to a denial of service, caused by an issue when relying on unauthenticated IPv4 time sources in ntpd. By predicting transmit timestamps for use in spoofed packets, a remote attacker could exploit this vulnerability to cause the daemon to crash or system time change.
CVSS Base score: 7.4
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/183494 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H)

CVEID:CVE-2020-11868
**DESCRIPTION:**NTP is vulnerable to a denial of service, caused by a flaw in ntpd. By sending a server mode packet with a spoofed source IP address, a remote attacker could exploit this vulnerability to block unauthenticated synchronization resulting in a denial of service condition.
CVSS Base score: 5.9
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/180011 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H)

Affected Products and Versions

The vulnerabilities in the following filesets are being addressed:

To find out whether the affected filesets are installed on your systems, refer to the lslpp command found in AIX user’s guide.

Example: lslpp -L | grep -i ntp.rte

Remediation/Fixes

A. APARS

IBM has assigned the following APARs to this problem:

Subscribe to the APARs here:

<https://www.ibm.com/support/pages/apar/IJ26684&gt;

By subscribing, you will receive periodic email alerting you to the status of the APAR, and a link to download the fix once it becomes available.

B. FIXES

AIX fixes are available.

The AIX fixes can be downloaded via ftp or http from:

<ftp://aix.software.ibm.com/aix/efixes/security/ntp_fix13.tar&gt;
<http://aix.software.ibm.com/aix/efixes/security/ntp_fix13.tar&gt;
<https://aix.software.ibm.com/aix/efixes/security/ntp_fix13.tar&gt;

The link above is to a tar file containing this signed advisory, fix packages, and OpenSSL signatures for each package. The fixes below include prerequisite checking. This will enforce the correct mapping between the fixes and AIX Technology Levels.

To extract the fixes from the tar file:

tar xvf ntp_fix13.tar
cd ntp_fix13

Verify you have retrieved the fixes intact:

The checksums below were generated using the “openssl dgst -sha256 file” command as the following:

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 at <http://ibm.com/support/&gt; and describe the discrepancy.

openssl dgst -sha1 -verify [pubkey_file] -signature [advisory_file].sig [advisory_file]

openssl dgst -sha1 -verify [pubkey_file] -signature [ifix_file].sig [ifix_file]

Published advisory OpenSSL signature file location:

<http://aix.software.ibm.com/aix/efixes/security/ntp_advisory13.asc.sig&gt;
<https://aix.software.ibm.com/aix/efixes/security/ntp_advisory13.asc.sig&gt;
<ftp://aix.software.ibm.com/aix/efixes/security/ntp_advisory13.asc.sig&gt;

C. FIX AND INTERIM FIX INSTALLATION

If possible, it is recommended that a mksysb backup of the system be created. Verify it is both bootable and readable before proceeding.

The fix will not take affect until any running xntpd servers have been stopped and restarted with the following commands:

stopsrc -s xntpd
startsrc -s xntpd

To preview a fix installation:

installp -a -d fix_name -p all # where fix_name is the name of the

fix package being previewed.

To install a fix package:

installp -a -d fix_name -X all # where fix_name is the name of the

fix package being installed.

After installation the ntp daemon must be restarted:

stopsrc -s xntpd
startsrc -s xntpd

Interim fixes have had limited functional and regression testing but not the full regression testing that takes place for Service Packs; however, IBM does fully support them.

Interim fix management documentation can be found at:

<http://www14.software.ibm.com/webapp/set2/sas/f/aix.efixmgmt/home.html&gt;

To preview an interim fix installation:

emgr -e ipkg_name -p # where ipkg_name is the name of the

interim fix package being previewed.

To install an interim fix package:

emgr -e ipkg_name -X # where ipkg_name is the name of the

interim fix package being installed.

Workarounds and Mitigations

None