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libexpat CVE-2026-56405

| EUVDEUVD-2026-38182 MEDIUM
Integer Overflow or Wraparound (CWE-190)
2026-06-21 mitre GHSA-hqmj-33cm-gqpq
Integer Overflow Buffer Overflow Libexpat Red Hat 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

AV:L and AC:H reflect that triggering INT_MAX overflow requires crafted local XML input under specific attribute-count conditions; C:H/I:H from memory corruption potential.

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
Red Hat
4.9 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 getAttributeId.

AnalysisAI

Integer overflow in libexpat's getAttributeId routine exposes any application embedding libexpat before version 2.8.2 to memory corruption with high confidentiality and integrity impact when parsing specially crafted XML documents. The flaw occurs when an internal counter traversing the attribute ID table reaches INT_MAX and wraps, producing an invalid index that can corrupt adjacent heap memory. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Craft XML with extreme attribute ID collisions
Delivery
Supply document to libexpat-parsing application
Exploit
getAttributeId counter reaches INT_MAX
Execution
Signed integer wraps to negative value
Persist
Out-of-bounds heap write
Impact
Arbitrary code execution in application context
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Vulnerability AssessmentAI

Exploitation The vulnerability is triggered during attribute ID resolution within the XML parser when the internal counter i in getAttributeId reaches INT_MAX. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The official CVSS 3.1 score of 6.9 with vector AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L reflects a carefully calibrated medium-high risk. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker crafts an XML document containing a pathologically large number of attribute declarations - potentially exploiting XML namespace mechanics to force repeated attribute ID lookups - and delivers it to an application that uses libexpat for parsing (e.g., a local file processor or a network service accepting XML input). When getAttributeId processes this document, the loop counter wraps past INT_MAX, producing an invalid memory reference that can overwrite adjacent heap data and potentially redirect execution flow. …
Remediation Upgrade to libexpat 2.8.2, which introduces the INT_MAX guard in getAttributeId as documented in the upstream fix at https://github.com/libexpat/libexpat/pull/1251. … Detailed patch versions, workarounds, and compensating controls in full report.
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Same weakness CWE-190 – Integer Overflow or Wraparound

View all
CVE-2013-2729 CRITICAL POC
9.8
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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-2026-56405 vulnerability details – vuln.today
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