Summary

There is a vulnerability in NTPv3 and NTPv4 that affects AIX.

Vulnerability Details

CVEID: CVE-2019-8936 DESCRIPTION: NTP is vulnerable to a denial of service, caused by a NULL pointer dereference in ntp_control.c. By sending specially crafted mode 6 packets, a remote authenticated attacker could exploit this vulnerability to cause the ntpd daemon to SIGSEGV.
CVSS Base Score: 5.3
CVSS Temporal Score: See <https://exchange.xforce.ibmcloud.com/vulnerabilities/158926&gt; for the current score
CVSS Environmental Score*: Undefined
CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H)

Affected Products and Versions

AIX 7.1, 7.2
VIOS 2.2, 3.1

The vulnerabilities in the following filesets are being addressed:

key_fileset = aix

For NTPv3:

Fileset Lower Level Upper Level KEY PRODUCT(S)
---------------------------------------------------------------------
bos.net.tcp.client 6.1.9.0 6.1.9.403 key_w_fs NTPv3
bos.net.tcp.client 7.1.4.0 7.1.4.35 key_w_fs NTPv3
bos.net.tcp.client 7.1.5.0 7.1.5.33 key_w_fs NTPv3
bos.net.tcp.ntpd 7.2.1.0 7.2.1.3 key_w_fs NTPv3
bos.net.tcp.ntpd 7.2.2.0 7.2.2.17 key_w_fs NTPv3
bos.net.tcp.ntpd 7.2.3.0 7.2.3.15 key_w_fs NTPv3

For NTPv4:

Fileset Lower Level Upper Level KEY PRODUCT(S)
---------------------------------------------------------------------
ntp.rte 7.4.2.8100 7.4.2.8121 key_w_fs NTPv4

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 bos.net.tcp.client

Remediation/Fixes

A. APARS

IBM has assigned the following APARs to this problem:

For NTPv3:

AIX Level APAR Availability SP KEY PRODUCT(S)
------------------------------------------------------------
7.1.4 IJ17061 ** N/A key_w_apar NTPv3
7.1.5 IJ17062 ** SP5 key_w_apar NTPv3
7.2.1 IJ17063 ** N/A key_w_apar NTPv3
7.2.2 IJ17064 ** SP5 key_w_apar NTPv3
7.2.3 IJ17065 ** SP4 key_w_apar NTPv3

VIOS Level APAR Availability SP KEY PRODUCT(S)
----------------------------------------------------------------
2.2.5 IJ17060 ** N/A key_w_apar NTPv3
2.2.6 IJ17060 ** 2.2.6.50 key_w_apar NTPv3
3.1.0 IJ17065 ** 3.1.0.30 key_w_apar NTPv3

For NTPv4:

AIX Level APAR Availability SP KEY PRODUCT(S)
------------------------------------------------------------
7.1.4 IJ17059 ** N/A key_w_apar NTPv4
7.1.5 IJ17059 ** SP5 key_w_apar NTPv4
7.2.1 IJ17059 ** N/A key_w_apar NTPv4
7.2.2 IJ17059 ** SP5 key_w_apar NTPv4
7.2.3 IJ17059 ** SP4 key_w_apar NTPv4

VIOS Level APAR Availability SP KEY PRODUCT(S)
----------------------------------------------------------------
2.2.5 IJ17059 ** N/A key_w_apar NTPv4
2.2.6 IJ17059 ** 2.2.6.50 key_w_apar NTPv4
3.1.0 IJ17059 ** 3.1.0.30 key_w_apar NTPv4

Subscribe to the APARs here:

https://www.ibm.com/support/docview.wss?uid=isg1IJ17060
https://www.ibm.com/support/docview.wss?uid=isg1IJ17061
https://www.ibm.com/support/docview.wss?uid=isg1IJ17062
https://www.ibm.com/support/docview.wss?uid=isg1IJ17063
https://www.ibm.com/support/docview.wss?uid=isg1IJ17064
https://www.ibm.com/support/docview.wss?uid=isg1IJ17065
https://www.ibm.com/support/docview.wss?uid=isg1IJ17059

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 and VIOS fixes are available. The AIX/VIOS fixes can be downloaded via ftp or http from:

ftp://aix.software.ibm.com/aix/efixes/security/ntp_fix12.tar
http://aix.software.ibm.com/aix/efixes/security/ntp_fix12.tar
https://aix.software.ibm.com/aix/efixes/security/ntp_fix12.tar

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.

For NTPv3:
AIX Level Interim Fix (*.Z) KEY PRODUCT(S)
----------------------------------------------------------
7.1.4.6 IJ17061m8a.190628.epkg.Z key_w_fix NTPv3
7.1.4.7 IJ17061m8a.190628.epkg.Z key_w_fix NTPv3
7.1.4.8 IJ17061m8a.190628.epkg.Z key_w_fix NTPv3
7.1.5.2 IJ17062m4a.190628.epkg.Z key_w_fix NTPv3
7.1.5.3 IJ17062m4a.190628.epkg.Z key_w_fix NTPv3
7.1.5.4 IJ17062m4a.190628.epkg.Z key_w_fix NTPv3
7.2.1.4 IJ17063m6a.190701.epkg.Z key_w_fix NTPv3
7.2.1.5 IJ17063m6a.190701.epkg.Z key_w_fix NTPv3
7.2.1.6 IJ17063m6a.190701.epkg.Z key_w_fix NTPv3
7.2.2.2 IJ17064m4a.190701.epkg.Z key_w_fix NTPv3
7.2.2.3 IJ17064m4a.190701.epkg.Z key_w_fix NTPv3
7.2.2.4 IJ17064m4a.190701.epkg.Z key_w_fix NTPv3
7.2.3.1 IJ17065m3a.190701.epkg.Z key_w_fix NTPv3
7.2.3.2 IJ17065m3a.190701.epkg.Z key_w_fix NTPv3
7.2.3.3 IJ17065m3a.190701.epkg.Z key_w_fix NTPv3

Please note that the above table refers to AIX TL/SP level as opposed to fileset level, i.e., 7.2.2.2 is AIX 7200-02-02.

VIOS Level Interim Fix (*.Z) KEY PRODUCT(S)
-----------------------------------------------------------
2.2.5.40 IJ17060m9a.190628.epkg.Z key_w_fix NTPv3
2.2.5.50 IJ17060m9a.190628.epkg.Z key_w_fix NTPv3
2.2.5.60 IJ17060m9a.190628.epkg.Z key_w_fix NTPv3
2.2.6.20 IJ17060m9a.190628.epkg.Z key_w_fix NTPv3
2.2.6.21 IJ17060m9a.190628.epkg.Z key_w_fix NTPv3
2.2.6.23 IJ17060m9a.190628.epkg.Z key_w_fix NTPv3
2.2.6.30 IJ17060m9a.190628.epkg.Z key_w_fix NTPv3
2.2.6.31 IJ17060m9a.190628.epkg.Z key_w_fix NTPv3
2.2.6.32 IJ17060m9a.190628.epkg.Z key_w_fix NTPv3
2.2.6.40 IJ17060m9a.190628.epkg.Z key_w_fix NTPv3
2.2.6.41 IJ17060m9a.190628.epkg.Z key_w_fix NTPv3
3.1.0.0 IJ17065m3a.190701.epkg.Z key_w_fix NTPv3
3.1.0.10 IJ17065m3a.190701.epkg.Z key_w_fix NTPv3
3.1.0.20 IJ17065m3a.190701.epkg.Z key_w_fix NTPv3
3.1.0.21 IJ17065m3a.190701.epkg.Z key_w_fix NTPv3

For NTPv4:

AIX Level Interim Fix (*.Z) KEY PRODUCT(S)
----------------------------------------------------------
7.1.x IJ17059m9b.190719.epkg.Z key_w_fix NTPv4
7.2.x IJ17059m9b.190719.epkg.Z key_w_fix NTPv4

VIOS Level Interim Fix (*.Z) KEY PRODUCT(S)
-----------------------------------------------------------
2.2.x IJ17059m9b.190719.epkg.Z key_w_fix NTPv4
3.1.0.x IJ17059m9b.190719.epkg.Z key_w_fix NTPv4

To extract the fixes from the tar file:

tar xvf ntp_fix12.tar
cd ntp_fix12

Verify you have retrieved the fixes intact:

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

openssl dgst -sha256 filename KEY
-----------------------------------------------------------------------------------------------------
5543f8cfe79e9b260b1ffd795f1e755d063564cb436e77b56ccf3c806378d2ca IJ17059m9b.190719.epkg.Z key_w_csum
fa9702b1406fd3b1437ac333f4a5a35cc8c8b6322a83970fbed6cf3f0ea73d5d IJ17060m9a.190628.epkg.Z key_w_csum
6b15b60f21f0a6e9506373ac5178aaf6a11e12a54087b27120614641222d0c48 IJ17061m8a.190628.epkg.Z key_w_csum
97e5c6ff951552e0b88a7ea61cf4b368844ae9d72721d923176f3c55b7340a0a IJ17062m4a.190628.epkg.Z key_w_csum
cd980f0e6ef7c69e5d1ad48eeb4bfc6f621a34747af28bf2c3e161e89fce251b IJ17063m6a.190701.epkg.Z key_w_csum
fa52c67254367424a611a269932b6de63c1d404ed9dd6cfa79eab465b91f11c6 IJ17064m4a.190701.epkg.Z key_w_csum
71bfbe4fb5697bc18d5a5d5524c9d64f08040aea04de765d1c1183c532006ef7 IJ17065m3a.190701.epkg.Z key_w_csum

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/ 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_advisory12.asc.sig
https://aix.software.ibm.com/aix/efixes/security/ntp_advisory12.asc.sig
ftp://aix.software.ibm.com/aix/efixes/security/ntp_advisory12.asc.sig

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

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.