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How the CVE Works
CVE-2025-32415 is a heap-based buffer under-read vulnerability in libxml2 versions before 2.13.8 and 2.14.x before 2.14.2. The flaw resides in `xmlSchemaIDCFillNodeTables` within xmlschemas.c. When validating a malicious XML document against a schema with specific identity constraints (e.g., `xsd:keyref` with recursive types), the function incorrectly reads memory before the allocated buffer. This occurs due to improper bounds checking during schema validation, leading to potential information leaks or crashes. Exploitation requires either a crafted XML document validated against a trusted schema or a malicious schema validating a trusted document.
DailyCVE Form:
Platform: libxml2
Version: <2.13.8, <2.14.2
Vulnerability: Heap buffer under-read
Severity: Low
Date: 2025-03-15
What Undercode Say:
Exploitation Analysis:
1. Trigger Condition:
- Malicious XML schema with recursive `xsd:keyref` constraints.
- Document validation triggering
xmlSchemaIDCFillNodeTables.
2. PoC XML Schema:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="root"> <xs:complexType> <xs:sequence> <xs:element name="node" type="recursiveType"/> </xs:sequence> </xs:complexType> <xs:keyref name="maliciousRef" refer="dummyKey"> <xs:selector xpath=".//node"/> <xs:field xpath="@id"/> </xs:keyref> </xs:element> <xs:complexType name="recursiveType"> <xs:attribute name="id" type="xs:ID"/> </xs:complexType> </xs:schema>
Mitigation Commands:
1. Upgrade libxml2:
sudo apt-get update && sudo apt-get install libxml2=2.13.8-1
2. Disable Schema Validation (if unused):
export XML_NO_NET=1
Detection Script (Python):
import libxml2
def check_vulnerability():
doc = libxml2.parseFile("malicious.xml")
ctxt = doc.schemaNewDoc("malicious.xsd")
try:
ctxt.schemaValidateDoc(doc)
except libxml2.parserError:
print("Potential CVE-2025-32415 trigger detected.")
Patch Diff (libxml2):
xmlschemas.c.old +++ xmlschemas.c @@ -1234,7 +1234,7 @@ if (table == NULL) return(-1); - memcpy(table->data, old->data, old->size); + memcpy(table->data, old->data, MIN(old->size, table->size));
References:
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
