Summary

There is a vulnerability in FreeBSD that affects AIX.

Vulnerability Details

CVEID: CVE-2018-6922 DESCRIPTION: FreeBSD is vulnerable to a denial of service, caused by the use of an inefficient TCP reassembly algorithm. By sending specially-crafted TCP traffic, a remote attacker could exploit this vulnerability to consume all available CPU resources.
CVSS Base Score: 7.5
CVSS Temporal Score: See <https://exchange.xforce.ibmcloud.com/vulnerabilities/148026&gt; for the current score
CVSS Environmental Score*: Undefined
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Affected Products and Versions

AIX 5.3, 6.1, 7.1, 7.2
VIOS 2.2.x

The following fileset levels are vulnerable:

key_fileset = aix

Fileset Lower Level Upper Level KEY
---------------------------------------------------------
bos.net.tcp.client 5.3.12.0 5.3.12.10 key_w_fs
bos.perf.perfstat 5.3.12.0 5.3.12.2 key_w_fs
bos.net.tcp.client 6.1.9.0 6.1.9.401 key_w_fs
bos.perf.perfstat 6.1.9.0 6.1.9.400 key_w_fs
bos.net.tcp.client 7.1.4.0 7.1.4.34 key_w_fs
bos.perf.perfstat 7.1.4.0 7.1.4.31 key_w_fs
bos.net.tcp.client 7.1.5.0 7.1.5.31 key_w_fs
bos.perf.perfstat 7.1.5.0 7.1.5.30 key_w_fs
bos.net.tcp.client_core 7.2.0.0 7.2.0.5 key_w_fs
bos.perf.perfstat 7.2.0.0 7.2.0.2 key_w_fs
bos.net.tcp.client_core 7.2.1.0 7.2.1.4 key_w_fs
bos.perf.perfstat 7.2.1.0 7.2.1.1 key_w_fs
bos.net.tcp.client_core 7.2.2.0 7.2.2.17 key_w_fs
bos.perf.perfstat 7.2.2.0 7.2.2.16 key_w_fs
bos.net.tcp.client_core 7.2.3.0 7.2.3.15 key_w_fs
bos.perf.perfstat 7.2.3.0 7.2.3.0 key_w_fs

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.rte

Remediation/Fixes

A. APARS

IBM has assigned the following APARs to this problem:

AIX Level APAR Availability SP KEY
------------------------------------------------
5.3.12 IJ09618 ** N/A key_w_apar
6.1.9 IJ09619 ** N/A key_w_apar
7.1.4 IJ09620 ** SP8 key_w_apar
7.1.5 IJ09621 ** SP4 key_w_apar
7.2.0 IJ09622 ** N/A key_w_apar
7.2.1 IJ09623 ** SP6 key_w_apar
7.2.2 IJ09624 ** SP4 key_w_apar
7.2.3 IJ09625 ** SP3 key_w_apar

VIOS Level APAR Availability SP KEY
----------------------------------------------------
2.2.4 IJ09619 ** N/A key_w_apar
2.2.5 IJ09619 ** 2.2.5.50 key_w_apar
2.2.6 IJ09619 ** 2.2.6.40 key_w_apar
3.1.0 IJ09625 ** 3.1.0.20 key_w_apar

Subscribe to the APARs here:

http://www.ibm.com/support/docview.wss?uid=isg1IJ09618
http://www.ibm.com/support/docview.wss?uid=isg1IJ09619
http://www.ibm.com/support/docview.wss?uid=isg1IJ09620
http://www.ibm.com/support/docview.wss?uid=isg1IJ09621
http://www.ibm.com/support/docview.wss?uid=isg1IJ09622
http://www.ibm.com/support/docview.wss?uid=isg1IJ09623
http://www.ibm.com/support/docview.wss?uid=isg1IJ09624
http://www.ibm.com/support/docview.wss?uid=isg1IJ09625

https://www.ibm.com/support/docview.wss?uid=isg1IJ09618
https://www.ibm.com/support/docview.wss?uid=isg1IJ09619
https://www.ibm.com/support/docview.wss?uid=isg1IJ09620
https://www.ibm.com/support/docview.wss?uid=isg1IJ09621
https://www.ibm.com/support/docview.wss?uid=isg1IJ09622
https://www.ibm.com/support/docview.wss?uid=isg1IJ09623
https://www.ibm.com/support/docview.wss?uid=isg1IJ09624
https://www.ibm.com/support/docview.wss?uid=isg1IJ09625

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.

An LPAR system reboot is required to complete the iFix installation, or Live Update may be used on AIX 7.2 to avoid a reboot.

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

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

AIX Level Interim Fix (*.Z) KEY
----------------------------------------------
5.3.12.9 IJ09618s9a.181031.epkg.Z key_w_fix
6.1.9.10 IJ09619sAa.181004.epkg.Z key_w_fix
6.1.9.11 IJ09619sBa.181004.epkg.Z key_w_fix
6.1.9.12 IJ09619sCa.181009.epkg.Z key_w_fix
7.1.4.4 IJ09620s4a.180927.epkg.Z key_w_fix
7.1.4.5 IJ09620s5a.180927.epkg.Z key_w_fix
7.1.4.6 IJ09620s6a.180926.epkg.Z key_w_fix
7.1.5.1 IJ09621s1a.180926.epkg.Z key_w_fix
7.1.5.2 IJ09621s2a.180925.epkg.Z key_w_fix
7.1.5.3 IJ09621s3a.181001.epkg.Z key_w_fix
7.2.0.4 IJ09622s4a.181001.epkg.Z key_w_fix
7.2.0.5 IJ09622s5a.181001.epkg.Z key_w_fix
7.2.0.6 IJ09622s6a.181001.epkg.Z key_w_fix
7.2.1.2 IJ09623s2a.181002.epkg.Z key_w_fix
7.2.1.3 IJ09623s3a.181002.epkg.Z key_w_fix
7.2.1.4 IJ09623s4a.181002.epkg.Z key_w_fix
7.2.2.0 IJ09624s0a.181002.epkg.Z key_w_fix
7.2.2.1 IJ09624s1a.181003.epkg.Z key_w_fix
7.2.2.2 IJ09624s2a.181003.epkg.Z key_w_fix
7.2.3.0 IJ09625s0a.181010.epkg.Z key_w_fix
7.2.3.1 IJ09625s0a.181010.epkg.Z key_w_fix
7.2.3.2 IJ09625s2a.181203.epkg.Z key_w_fix

Please note that the above table refers to AIX TL/SP level as opposed to fileset level, i.e., 7.2.2.1 is AIX 7200-02-01.

Please reference the Affected Products and Version section above for help with checking installed fileset levels.

VIOS Level Interim Fix (*.Z) KEY
-----------------------------------------------
2.2.4.60 IJ09619sBa.181004.epkg.Z key_w_fix
2.2.5.40 IJ09619sBa.181004.epkg.Z key_w_fix
2.2.6.23 IJ09619sBa.181004.epkg.Z key_w_fix
2.2.6.30 IJ09619sCa.181009.epkg.Z key_w_fix
2.2.6.31 IJ09619sCa.181009.epkg.Z key_w_fix
2.2.6.32 IJ09619sCa.181009.epkg.Z key_w_fix
3.1.0.0 IJ09625s2a.181203.epkg.Z key_w_fix
3.1.0.10 IJ09625s2a.181203.epkg.Z key_w_fix

To extract the fixes from the tar file:

tar xvf freebsd_fix.tar
cd freebsd_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 KEY
-----------------------------------------------------------------------------------------------------
b5c7014035793e7f6be1282d60e8f41513acd3b812d3f698dead8e6a34c33836 IJ09618s9a.181031.epkg.Z key_w_csum
05ae1d9525cf04571eb9d52ae48286c8e8b8563629cc5f025cf6bdc2a3c31bef IJ09619sAa.181004.epkg.Z key_w_csum
60052520a6b91171433cc6775677561d7c4805922f5e71b9021567804cbf5839 IJ09619sBa.181004.epkg.Z key_w_csum
61290b161399924a9ff401053ebd3b5ee653f0a08fb32af283320310ce8dc76b IJ09619sCa.181009.epkg.Z key_w_csum
8d4148216457891428b8fcd110d94227dd9052a38e5bbc7ec1c489ef26b7ec41 IJ09620s4a.180927.epkg.Z key_w_csum
ed8fb402bcc5e61ed66dd93d17e4bdb495ca84f96df056cde8a51faccec1890b IJ09620s5a.180927.epkg.Z key_w_csum
7775584ea7da80cd4cd8454cafbe3a942f6ec4e7952527905c9418d2d77a8614 IJ09620s6a.180926.epkg.Z key_w_csum
aa1ea66f3a99bd23ca0c66ce14b344ebebc0cfd693f03443f6d4b0003ce994f8 IJ09621s1a.180926.epkg.Z key_w_csum
a16276ac02280abc33df7edc338e7397a083a0e7cbdae2803f84d88338c0b542 IJ09621s2a.180925.epkg.Z key_w_csum
12185b57e2168aa1e89ceba842f01ae0ecc0c66034f979461a74bb0453917a89 IJ09621s3a.181001.epkg.Z key_w_csum
295a95d3de48b57da05e2a287845ec1fa30a5f6c1bc623bc112d8875d5e1f7f0 IJ09622s4a.181001.epkg.Z key_w_csum
7f453dbc597c80ddcb87c019a2fb258ded6258a81709d3a4c5ee4eca56d2588a IJ09622s5a.181001.epkg.Z key_w_csum
b46a7800fd8ca18eaba43c31741987d4928ad99daf9eaefeb14340befd22c059 IJ09622s6a.181001.epkg.Z key_w_csum
fa7950e628b4d76a1c00865f4e5b4a8e514663a79f5cb2f7497b5d2099828f3f IJ09623s2a.181002.epkg.Z key_w_csum
ec15d06abdae9169cef5596dbe3e7a77216bd5e3af3066fc0562b4a5e9599a6c IJ09623s3a.181002.epkg.Z key_w_csum
871348aff03053c4ba0f9b46ca0bbe768513bd64000820f42161fba485fc836c IJ09623s4a.181002.epkg.Z key_w_csum
73062bc6662e52f6965c2ac4af6a2ac090046e808446920e1a33d477fe96a4c1 IJ09624s0a.181002.epkg.Z key_w_csum
e5ee7b489eea99c92765546c8be6a1ac13779d83107d9e70785862148d6fd7de IJ09624s1a.181003.epkg.Z key_w_csum
33d0d44b86f3d00629ef232bc71490e1f2d6b8342c39e1d9ac034c9a0d16c5a0 IJ09624s2a.181003.epkg.Z key_w_csum
2166aefe2baebce7d3982f7e091620f9cf97e66ad39711954313b9130e93e3fc IJ09625s0a.181010.epkg.Z key_w_csum
714621b65a901d87f07565897763e907095812719a4f465b7a1170074b4c5f95 IJ09625s2a.181203.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/freebsd_advisory.asc.sig
https://aix.software.ibm.com/aix/efixes/security/freebsd_advisory.asc.sig
ftp://aix.software.ibm.com/aix/efixes/security/freebsd_advisory.asc.sig

C. FIX AND INTERIM FIX INSTALLATION

An LPAR system reboot is required to complete the iFix installation, or Live Update may be used on AIX 7.2 to avoid a reboot.

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

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.

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.