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libexpat CVE-2026-56404

| EUVDEUVD-2026-38181 MEDIUM
Integer Overflow or Wraparound (CWE-190)
2026-06-21 mitre GHSA-h5j3-rr49-jmm6
Integer Overflow Buffer Overflow Libexpat Suse
6.9
CVSS 3.1 · NVD
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Severity by source

Vendor (mitre) PRIMARY
MEDIUM
qualitative
NVD
6.9 MEDIUM
AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
vuln.today AI
6.9 MEDIUM

Signed integer overflow requires precision-crafted XML to reach INT_MAX (AC:H); no OS privileges needed for the parse path (PR:N); AV:L per vendor and NVD assessment; A:L reflects partial rather than full availability disruption.

3.1 AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
4.0 AV:L/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
SUSE
MEDIUM
qualitative

Primary rating from Vendor (mitre).

CVSS VectorNVD

CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
Attack Vector
Local
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
Low

Lifecycle Timeline

3
Source Code Evidence Fetched
Jun 22, 2026 - 06:40 vuln.today
Analysis Generated
Jun 22, 2026 - 06:40 vuln.today
Patch available
Jun 21, 2026 - 17:01 EUVD

DescriptionNVD

libexpat before 2.8.2 has an integer overflow in addBinding.

AnalysisAI

Integer overflow in libexpat's addBinding function (xmlparse.c) before version 2.8.2 allows memory corruption during XML namespace binding processing, with high confidentiality and integrity impact. All libexpat releases from 0 through 2.8.2-pre are affected (CPE: cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*), encompassing a significant downstream attack surface given the library's widespread use in Python, PHP, and system utilities. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Craft XML with excessive namespace bindings
Delivery
Deliver malicious XML to libexpat-based application
Exploit
Trigger addBinding with len reaching INT_MAX
Execution
Signed integer overflow corrupts heap
Impact
Achieve code execution or sensitive data disclosure
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Vulnerability AssessmentAI

Exploitation Exploitation requires all of the following: (1) the target application links against libexpat prior to 2.8.2; (2) the application processes XML input that includes namespace binding declarations (`xmlns:` attributes), which invokes the `addBinding` code path; (3) the attacker can supply XML crafted to accumulate namespace bindings until `len` reaches INT_MAX - a high-complexity condition (AC:H) that is not trivially reproducible. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.1 vector AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L yields a 6.9 Medium score, and the signal composition is internally consistent. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker engineers a malicious XML document with a large volume of namespace binding declarations deliberately crafted to push the `len` counter in `addBinding` to INT_MAX, triggering signed integer overflow on the next increment and corrupting heap metadata. If this malicious document is supplied to a local application - such as a file-format converter, document processor, or configuration parser using libexpat - the resulting memory corruption could yield arbitrary code execution within the process. …
Remediation The primary fix is upgrading to libexpat 2.8.2 or later, which incorporates the integer overflow guards in `addBinding`. … Detailed patch versions, workarounds, and compensating controls in full report.
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Same weakness CWE-190 – Integer Overflow or Wraparound

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CVE-2013-2729 CRITICAL POC
9.8
CVE-2015-8651 HIGH
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CVE-2012-5054 HIGH POC
8.8
CVE-2014-0569 CRITICAL POC
9.3
CVE-2017-3599 HIGH POC
7.5
CVE-2017-7529 HIGH
7.5
CVE-2016-1010 HIGH
8.8
CVE-2013-3940 CRITICAL
9.3

Same technique Integer Overflow

View all
CVE-2014-0497 CRITICAL POC
9.8
CVE-2013-2729 CRITICAL POC
9.8
CVE-2015-8651 HIGH
8.8
CVE-2012-5054 HIGH POC
8.8
CVE-2014-0569 CRITICAL POC
9.3
CVE-2017-3599 HIGH POC
7.5
CVE-2017-7529 HIGH
7.5
CVE-2016-1010 HIGH
8.8

Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SLES15-SP5-CHOST-BYOS-SAP-CCloud Not-Affected
SLES15-SP5-CHOST-BYOS-SAP-CCloud Affected
SLES15-SP6-CHOST-BYOS Affected
SLES15-SP6-CHOST-BYOS-Aliyun Affected
SLES15-SP6-CHOST-BYOS-Azure Affected

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CVE-2026-56404 vulnerability details – vuln.today
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