Security Bulletin: AIX is vulnerable to denial of service due to ISC BIND

Security Bulletin

Summary

UPDATED: (Corrected the affected fileset levels to reflect that bind.rte 7.1.916.2604 and 7.3.916.2601 are vulnerable) Multiple vulnerabilities in ISC BIND could allow a remote attacker to cause a denial of service. AIX uses ISC BIND as part of its DNS functions.

Vulnerability Details

CVEID: CVE-2023-50868
DESCRIPTION: ISC BIND is vulnerable to a denial of service, caused by an error when preparing an NSEC3 closest encloser proof. By flooding the target resolver with queries, a remote attacker could exploit this vulnerability to cause CPU exhaustion on a DNSSEC-validating resolver.
CVSS Base score: 7.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/282901 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-2023-50387
DESCRIPTION: Microsoft Windows is vulnerable to a denial of service, caused by improper restriction of DNSSEC verification complexity. By conducting an attack leveraging a highly complex DNSSEC verification framework, a remote attacker could exploit this vulnerability to exhaust CPU resources and stall DNS resolvers, resulting in a denial of service.
CVSS Base score: 7.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/281081 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-2023-4408
DESCRIPTION: ISC BIND is vulnerable to a denial of service, caused by an error when parsing large DNS messages. By flooding the target server with queries, a remote attacker could exploit this vulnerability to cause excessive CPU load.
CVSS Base score: 7.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/282906 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-2023-6516
DESCRIPTION: ISC BIND is vulnerable to a denial of service, caused by an out-of-memory condition. By using specific recursive query patterns, a remote attacker could exploit this vulnerability to cause the amount of memory used by a named resolver to go well beyond the configured max-cache-size limit, leading to a denial of service.
CVSS Base score: 7.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/282902 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-2023-5679
DESCRIPTION: ISC BIND is vulnerable to a denial of service, caused by an error when enabling both DNS64 and serve-stale. By querying a DNS64-enabled resolver for domain names triggering serve-stale, a remote attacker could exploit this vulnerability to trigger an assertion failure.
CVSS Base score: 7.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/282904 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-2023-5517
DESCRIPTION: ISC BIND is vulnerable to a denial of service, caused by a flaw in query-handling code. By querying RFC 1918 reverse zones, a remote attacker could exploit this vulnerability to trigger an assertion failure.
CVSS Base score: 7.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/282905 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

Affected Product(s)	Version(s)
AIX	7.2
AIX	7.3
VIOS	3.1
VIOS	4.1

The following fileset levels are vulnerable:

Fileset	Lower Level	Upper Level
bind.rte	7.1.916.0	7.1.916.2604
bind.rte	7.2.916.0	7.2.916.2600
bind.rte	7.3.916.0	7.3.916.2601

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 bind.rte

Remediation/Fixes

A. FIXES

IBM strongly recommends addressing the vulnerability now.

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

https://aix.software.ibm.com/aix/efixes/security/bind_fix26.tar

The link above is to a tar file containing this signed advisory, install 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 bind_fix26.tar

For AIX 7.2 and VIOS 3.1 with OpenSSL 1.0 installed:

tar xvf bind_fix26/71bind916.tar

For AIX 7.2 and VIOS 3.1 with OpenSSL 1.1 installed:

tar xvf bind_fix26/72bind916.tar

For AIX 7.3 and VIOS 4.1:

tar xvf bind_fix26/73bind916.tar

IMPORTANT: 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 the fix installation:

installp -apYd . bind

To install the fix package:

installp -aXYd . bind

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
1a44cbf3ada06c29efdaad7757ab248995e0623689a5ca8682e4c610cd127364	71bind.rte
4016a2ffafda43b8deb9039dd6736a1b9bf3eb11afba0889041ae2e00dec5237	72bind.rte
4ed621e5f8957739023e370e04ef58bf38ee96489c6ba0f54181b40bcf239b8c	73bind.rte

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 -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/bind_advisory26.asc.sig

B. 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

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

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References

Complete CVSS v3 Guide
On-line Calculator v3

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Acknowledgement

Change History

05 Jun 2024: Corrected the affected fileset levels to reflect that bind.rte 7.1.916.2604 and 7.3.916.2601 are vulnerable.
04 Jun 2024: Initial Publication

*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.

Disclaimer

According to the Forum of Incident Response and Security Teams (FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry open standard designed to convey vulnerability severity and help to determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES ""AS IS"" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY. In addition to other efforts to address potential vulnerabilities, IBM periodically updates the record of components contained in our product offerings. As part of that effort, if IBM identifies previously unidentified packages in a product/service inventory, we address relevant vulnerabilities regardless of CVE date. Inclusion of an older CVEID does not demonstrate that the referenced product has been used by IBM since that date, nor that IBM was aware of a vulnerability as of that date. We are making clients aware of relevant vulnerabilities as we become aware of them. "Affected Products and Versions" referenced in IBM Security Bulletins are intended to be only products and versions that are supported by IBM and have not passed their end-of-support or warranty date. Thus, failure to reference unsupported or extended-support products and versions in this Security Bulletin does not constitute a determination by IBM that they are unaffected by the vulnerability. Reference to one or more unsupported versions in this Security Bulletin shall not create an obligation for IBM to provide fixes for any unsupported or extended-support products or versions.

Document Location

Worldwide

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Security Bulletin: AIX is vulnerable to denial of service due to ISC BIND