Summary

There are vulnerabilities in OpenSSL used by AIX.

Vulnerability Details

CVEID:CVE-2021-23839
**DESCRIPTION:**OpenSSL could provide weaker than expected security, caused by incorrect SSLv2 rollback protection that allows for the inversion of the logic during a padding check. If the server is configured for SSLv2 support at compile time, configured for SSLv2 support at runtime or configured for SSLv2 ciphersuites, it will accept a connection if a version rollback attack has occurred and erroneously reject a connection if a normal SSLv2 connection attempt is made.
CVSS Base score: 5.9
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/196849 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N)

CVEID:CVE-2021-23840
**DESCRIPTION:**OpenSSL is vulnerable to a denial of service, caused by an integer overflow in CipherUpdate. By sending an overly long argument, an attacker could exploit this vulnerability to cause the application to crash.
CVSS Base score: 7.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/196848 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

CVEID:CVE-2021-23841
**DESCRIPTION:**OpenSSL is vulnerable to a denial of service, caused by a NULL pointer dereference in the X509_issuer_and_serial_hash() function. By parsing the issuer field, an attacker could exploit this vulnerability to cause the application to crash.
CVSS Base score: 7.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/196847 for the current score.
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

The following fileset levels are vulnerable:

Note:

A. 0.9.8, 1.0.1 OpenSSL versions are out-of-support. Customers are advised to upgrade to currently supported OpenSSL 1.0.2 version.

B. Latest level of OpenSSL fileset is available from the web download site:

https://www-01.ibm.com/marketing/iwm/iwm/web/pickUrxNew.do?source=aixbp&S_PKG=openssl

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

Example: lslpp -L | grep -i openssl.base

Remediation/Fixes

A. FIXES

The fixes can be downloaded via ftp or http from:
<ftp://aix.software.ibm.com/aix/efixes/security/openssl_fix33.tar&gt;
<http://aix.software.ibm.com/aix/efixes/security/openssl_fix33.tar&gt;
<https://aix.software.ibm.com/aix/efixes/security/openssl_fix33.tar&gt;

The links above are 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.

Note that the tar file contains Interim fixes that are based on OpenSSL version, and AIX OpenSSL fixes are cumulative.

You must be on the ‘prereq for installation’ level before applying the interim fix. This may require installing a new level (prereq version) first.

To extract the fixes from the tar file:

tar xvf openssl_fix33.tar
cd openssl_fix33

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 AIX Support at <https://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/openssl_advisory33.asc.sig&gt;
<https://aix.software.ibm.com/aix/efixes/security/openssl_advisory33.asc.sig&gt;
ftp://aix.software.ibm.com/aix/efixes/security/openssl_advisory33.asc.s…

B. FIX AND INTERIM FIX INSTALLATION

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