CVE-2015-3931 in e-Szigno
Summary
by MITRE
Microsec e-Szigno before 3.2.7.12 allows remote attackers to perform XML signature wrapping attacks via an e-akta signed document with a ds:Object node with a crafted payload prepended to a valid ds:Object.
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Analysis
by VulDB Data Team • 12/13/2022
The vulnerability identified as CVE-2015-3931 affects Microsec e-Szigno software versions prior to 3.2.7.12, representing a critical security flaw in XML signature validation mechanisms. This vulnerability enables remote attackers to execute XML signature wrapping attacks against e-akta signed documents, which are commonly used in Hungarian digital signature systems. The flaw specifically targets the processing of ds:Object nodes within XML signatures, creating a pathway for malicious actors to manipulate signed documents without detection.
The technical implementation of this vulnerability stems from inadequate validation of XML signature structures during document processing. Attackers can prepend a crafted payload to a valid ds:Object node within an e-akta document, effectively wrapping the original signature with malicious content. This technique exploits the XML parsing behavior where the system processes the prepended content before the legitimate signature, allowing attackers to inject unauthorized data or commands while maintaining the appearance of a valid signature. The vulnerability falls under CWE-611 Improper Restriction of XML External Entity Reference, specifically manifesting as a failure to properly validate XML structure integrity during signature verification.
The operational impact of CVE-2015-3931 extends beyond simple document manipulation, as it undermines the fundamental trust model of digital signature systems. When exploited, this vulnerability can enable attackers to bypass authentication mechanisms, modify sensitive data, or inject malicious content into legally binding digital documents. The attack vector is particularly concerning because it operates remotely without requiring local system access, making it suitable for large-scale attacks against government or enterprise digital signature infrastructures. This vulnerability directly impacts the integrity and non-repudiation properties of digital signatures as defined by the X.509 standard and can compromise the security of entire digital signature ecosystems.
Organizations utilizing affected versions of Microsec e-Szigno should implement immediate mitigations including updating to version 3.2.7.12 or later, which contains proper XML signature validation controls. Additional protective measures include implementing strict XML schema validation, deploying XML security filters, and conducting regular signature integrity checks. From an att&ck framework perspective, this vulnerability maps to technique T1553.002 Subvert Trust Controls and T1068 Exploitation for Privilege Escalation, as attackers can leverage the signature wrapping to gain unauthorized access to systems or data. The vulnerability also aligns with the NIST SP 800-53 security controls, particularly those related to integrity protection and cryptographic key management, emphasizing the need for robust XML processing validation in digital signature systems.