Summary

Multiple vulnerabilities in NTP could allow a remote attacker to cause a denial of service (CVE-2023-26551, CVE-2023-26552, CVE-2023-26553, CVE-2023-26554).

Vulnerability Details

CVEID:CVE-2023-26551
**DESCRIPTION:**NTP is vulnerable to a denial of service, caused by an out-of-bounds write in mstolfp in libntp/mstolfp.c. By sending a specially-crafted request, a remote attacker could exploit this vulnerability to cause a denial of service.
CVSS Base score: 5.3
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/252595 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)

CVEID:CVE-2023-26552
**DESCRIPTION:**NTP is vulnerable to a denial of service, caused by an out-of-bounds write in mstolfp in libntp/mstolfp.c. By sending a specially-crafted request, a remote attacker could exploit this vulnerability to cause a denial of service.
CVSS Base score: 5.3
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/252594 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)

CVEID:CVE-2023-26553
**DESCRIPTION:**NTP is vulnerable to a denial of service, caused by an out-of-bounds write in mstolfp in libntp/mstolfp.c. By sending a specially-crafted request, a remote attacker could exploit this vulnerability to cause a denial of service.
CVSS Base score: 5.3
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/252593 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)

CVEID:CVE-2023-26554
**DESCRIPTION:**NTP is vulnerable to a denial of service, caused by an out-of-bounds write in mstolfp in libntp/mstolfp.c. By sending a specially-crafted request, a remote attacker could exploit this vulnerability to cause a denial of service.
CVSS Base score: 5.3
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/252592 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)

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/&gt;[APAR Number]

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

IBM strongly recommends addressing the vulnerability now.

AIX and VIOS fixes are available. The fixes are cumulative and address previously issued AIX/VIOS NTP security bulletins with respect to fileset level.

The AIX and VIOS fixes can be downloaded via https from:

<https://aix.software.ibm.com/aix/efixes/security/ntp_fix14.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_fix14.tar

cd ntp_fix14

Verify you have retrieved the fixes intact:

The checksums below were generated using the “openssl dgst -sha256 [filename]” 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 -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:

<https://aix.software.ibm.com/aix/efixes/security/ntp_advisory14.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.

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:

<https://www.ibm.com/support/pages/managing-interim-fixes-aix&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