CVE-2006-10003 in XML::Parser
Summary
by MITRE • 03/19/2026
XML::Parser versions through 2.47 for Perl has an off-by-one heap buffer overflow in st_serial_stack.
In the case (stackptr == stacksize - 1), the stack will NOT be expanded. Then the new value will be written at location (++stackptr), which equals stacksize and therefore falls just outside the allocated buffer.
The bug can be observed when parsing an XML file with very deep element nesting
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 04/21/2026
The vulnerability identified as CVE-2006-10003 affects XML::Parser versions through 2.47 for Perl, representing a critical heap buffer overflow condition that stems from improper memory management within the st_serial_stack implementation. This flaw manifests when processing XML documents containing extremely deep element nesting structures, creating a scenario where memory corruption can occur during parsing operations. The vulnerability specifically targets the stack management mechanism used by the XML parser to track element nesting levels, making it particularly dangerous in environments where untrusted XML content is processed. The issue is classified under CWE-121 as a heap-based buffer overflow, which falls within the broader category of memory safety vulnerabilities that can lead to arbitrary code execution or system compromise.
The technical implementation flaw occurs in the stack pointer management logic where the condition stackptr == stacksize - 1 is evaluated without proper expansion of the buffer before writing new values. When this condition is met, the system fails to allocate additional memory space, yet proceeds to increment the stack pointer and write data at the location (++stackptr), which equals the stacksize boundary. This off-by-one error results in writing beyond the allocated heap buffer, potentially corrupting adjacent memory regions and creating exploitable conditions. The vulnerability is particularly insidious because it only manifests under specific conditions involving deep XML nesting, making it difficult to detect during routine testing and potentially allowing attackers to craft payloads that trigger the overflow.
The operational impact of this vulnerability extends beyond simple parsing failures, as it creates a potential vector for remote code execution when XML::Parser is used in web applications, server-side processing systems, or any environment where XML content is parsed from untrusted sources. Attackers can exploit this vulnerability by crafting XML documents with deeply nested elements that force the parser to reach the buffer boundary condition, leading to memory corruption that may be leveraged for privilege escalation or system compromise. The vulnerability affects systems running Perl applications that utilize XML::Parser for processing XML data, including web services, content management systems, and enterprise applications that handle XML input. Organizations using affected versions face significant risk as this flaw can be exploited without requiring special privileges or complex attack vectors, making it particularly dangerous in production environments.
Mitigation strategies for CVE-2006-10003 should prioritize immediate patching of XML::Parser to versions that address the stack management logic and prevent the off-by-one condition. System administrators should also implement input validation measures that limit the depth of XML element nesting allowed in processing pipelines, effectively preventing exploitation through content restriction. Additionally, deploying application firewalls and intrusion detection systems that monitor for suspicious XML parsing patterns can provide additional defense layers. Organizations should consider implementing memory protection mechanisms such as stack canaries, address space layout randomization, and heap metadata protection to reduce the exploitability of similar buffer overflow conditions. The vulnerability demonstrates the importance of proper boundary checking in memory management operations and aligns with ATT&CK technique T1203, which covers exploitation of memory corruption vulnerabilities for privilege escalation. Regular security assessments and code reviews focusing on buffer management practices should be implemented to identify and remediate similar issues in other components of the system infrastructure.