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Security Bulletin: Multiple vulnerabilities in Python affects AIX/VIOS.

Security Bulletin


Summary

Integer overflow and use after may cause memory corruption and denial of service.

Vulnerability Details

CVEID:   CVE-2026-56403
DESCRIPTION:   libexpat before 2.8.2 has an integer overflow in storeAtts.
CWE:   CWE-190: Integer Overflow or Wraparound
CVSS Source:   NVD
CVSS Base score:   6.9
CVSS Vector:   (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L)

CVEID:   CVE-2026-56404
DESCRIPTION:   libexpat before 2.8.2 has an integer overflow in addBinding.
CWE:   CWE-190: Integer Overflow or Wraparound
CVSS Source:   NVD
CVSS Base score:   6.9
CVSS Vector:   (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L)

CVEID:   CVE-2026-56405
DESCRIPTION:   libexpat before 2.8.2 has an integer overflow in getAttributeId.
CWE:   CWE-190: Integer Overflow or Wraparound
CVSS Source:   NVD
CVSS Base score:   6.9
CVSS Vector:   (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L)

CVEID:   CVE-2026-56406
DESCRIPTION:   libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check that was present in XML_Parse.
CWE:   CWE-190: Integer Overflow or Wraparound
CVSS Source:   cve@mitre.org
CVSS Base score:   6.9
CVSS Vector:   (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L)

CVEID:   CVE-2026-56407
DESCRIPTION:   libexpat before 2.8.2 has an integer overflow in doProlog that is related to storeEntityValue and entity textLen.
CWE:   CWE-190: Integer Overflow or Wraparound
CVSS Source:   cve@mitre.org
CVSS Base score:   6.9
CVSS Vector:   (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L)

CVEID:   CVE-2026-56408
DESCRIPTION:   libexpat before 2.8.2 has an integer overflow in copyString.
CWE:   CWE-190: Integer Overflow or Wraparound
CVSS Source:   cve@mitre.org
CVSS Base score:   6.9
CVSS Vector:   (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L)

CVEID:   CVE-2026-56409
DESCRIPTION:   xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputDir is used.
CWE:   CWE-190: Integer Overflow or Wraparound
CVSS Source:   cve@mitre.org
CVSS Base score:   6.5
CVSS Vector:   (CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L)

CVEID:   CVE-2026-56410
DESCRIPTION:   xmlwf in libexpat before 2.8.2 has an integer overflow in resolveSystemId.
CWE:   CWE-190: Integer Overflow or Wraparound
CVSS Source:   cve@mitre.org
CVSS Base score:   6.9
CVSS Vector:   (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L)

CVEID:   CVE-2026-56411
DESCRIPTION:   xmlwf in libexpat before 2.8.2 has an integer overflow in endDoctypeDecl via NOTATION declarations.
CWE:   CWE-190: Integer Overflow or Wraparound
CVSS Source:   cve@mitre.org
CVSS Base score:   6.9
CVSS Vector:   (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L)

CVEID:   CVE-2026-56412
DESCRIPTION:   libexpat before 2.8.2 does not consider XML_TOK_DATA_CHARS in doCdataSection and thus lacks handler call depth tracking for various calls from within handlers in cases of a policy violation. Thus, a use-after-free can occur. NOTE: this issue exists because of an incomplete fix for CVE-2026-50219.
CWE:   CWE-416: Use After Free
CVSS Source:   NVD
CVSS Base score:   5.9
CVSS Vector:   (CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L)

Affected Products and Versions

AFFECTED PRODUCTS AND VERSIONS:
Affected Product(s)Version(s)
AIX7.3
VIOS4.1

 

The vulnerabilities in the following filesets are being addressed:

        key_fileset = osrcaix
FilesetLower LevelUpper Level
python3.9.base3.9.0.03.9.24.0
python3.11.base3.11.0.03.11.15.0

Note:

        A. Python 3.9 is out-of-support. Considering long term support, it is advised to upgrade to Python 3.11.

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

        https://www.ibm.com/resources/mrs/assets?source=aixbp

 

Remediation/Fixes

    REMEDIATION:

        A. FIXES

            IBM strongly recommends addressing the vulnerability now.

            The fixes can be downloaded via https from:

            https://aix.software.ibm.com/aix/efixes/security/python_fix20.tar

            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.
            

            AIX Level      Fix (*.Z)              KEY
            -----------------------------------------------
            7.3            python-3.11.15.1.tar.Z key_w_fix

            VIOS Level     Fix (*.Z)              KEY
            -----------------------------------------------
            4.1            python-3.11.15.1.tar.Z key_w_fix


            To extract the fixes from the tar file:

            tar xvf python_fix20.tar
            cd python_fix20

            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
            ---------------------------------------------------------------------------------------------------
            1c8bf8003e57165d2b46f2ba2eea35c03f5095dc95dbb49882e700d5f4edb1e0  python-3.11.15.1.tar.Z key_w_csum


            The checksums below were generated using the
            "openssl dgst -sha512 [filename]" command as the following:

            openssl dgst -sha512                                                                                                              filename
            ------------------------------------------------------------------------------------------------------------------------------------------------------------------------
            f08361d4d8b09c92e3b478a90c6f699dfa05f1b045ba2b6d0b9faa28aa9a7a0e1339c58c75f8346b17f15a4802d6b99b0804ba932b6207517cd7a13ec7a86b06  python-3.11.15.1.tar.Z key_4K_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 AIX Support at
            https://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/python_advisory20.asc.sig

        B. FIX AND INTERIM FIX INSTALLATION

            To extract the fixes from the tar file:

            zcat python-3.11.15.1.tar.Z | tar xvf -

            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 . python3.11.base

            To install the fix package:

            installp -aXYd . python3.11.base

Workarounds and Mitigations

None

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References

Complete CVSS v3 Guide
On-line Calculator v3

Off

Related Information

IBM Secure Engineering Web Portal
IBM Product Security Incident Response Blog

Acknowledgement

Change History

15 Jul 2026: 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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Document Information

Modified date:
15 July 2026

Initial Publish date:
15 July 2026

UID

ibm17280108

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