Security Bulletin
Summary
IBM ILOG CPLEX Optimization Studio uses libexpat as its built-in XML parser. This fix has addressed the following vulnerabilities in libexpat
Vulnerability Details
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-2026-56412
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 Product(s) | Version(s) |
| IBM ILOG CPLEX Optimization Studio (COS) | 22.2.0 |
| IBM ILOG CPLEX Optimization Studio (COS) | 22.1.2 |
| IBM ILOG CPLEX Optimization Studio (COS) | 22.1.1 |
| IBM ILOG CPLEX Optimization Studio (COS) | 22.1 |
| IBM ILOG CPLEX Optimization Studio (COS) | 20.1.0.1 |
| IBM ILOG CPLEX Optimization Studio (COS) | 20.1 |
| IBM ILOG CPLEX Optimization Studio (COS) | 12.10 |
| IBM ILOG CPLEX Optimization Studio (COS) | 12.9 |
Remediation/Fixes
1. You are required to upgrade to IBM ILOG CPLEX Optimization Studio to 22.2.0 in order to apply the fix
2. Download the fix from IBM ILOG CPLEX Optimization Studio 22.2.0.1 and follow the Install Instruction to apply the fix.
Workarounds and Mitigations
None
Get Notified about Future Security Bulletins
References
Acknowledgement
Change History
06 Nov 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:
06 November 2026
Initial Publish date:
06 November 2026
UID
ibm17295491