CVE-2026-59112 in libdigidocpp
Summary
by MITRE • 08/10/2026
Improper verification of cryptographic signature and Improper Check for Unusual or Exceptional Conditions vulnerability in Estonian Information System Authority (RIA) libdigidocpp, DigiDoc4, DigiDoc on Android, and DigiDoc on iOS. This issue affects libdigidocpp: from 4.1.0 before 4.2.1; DigiDoc4: from 4.7.0 before 4.8.2; DigiDoc on Android: from 2.7.0 before 2.7.2; DigiDoc on iOS: from 2.8.0 before 2.8.1.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability involves a critical weakness in cryptographic signature verification mechanisms within Estonian Information System Authority's digital signature libraries and applications, specifically affecting libdigidocpp version 4.1.0 through 4.2.0, DigiDoc4 versions 4.7.0 through 4.8.1, and mobile applications on both Android and iOS platforms. This issue stems from inadequate validation of digital signatures during the verification process, creating potential security risks that could allow malicious actors to bypass authentication mechanisms and compromise document integrity.
The technical flaw manifests as insufficient cryptographic signature verification procedures that fail to properly validate the authenticity and integrity of signed documents. The vulnerability specifically addresses improper check for unusual or exceptional conditions during signature validation, which falls under CWE-252 - "Unchecked Return Value" and CWE-347 - "Improper Verification of Cryptographic Signature." This weakness allows attackers to potentially submit malformed or tampered signatures that may pass validation checks due to the absence of proper exception handling and verification protocols.
The operational impact of this vulnerability extends across multiple platforms and applications, affecting both desktop and mobile environments used for digital signature processing in Estonia. The affected versions represent a significant attack surface since these libraries form the foundation for secure document signing processes in various governmental and institutional contexts. Attackers could exploit this weakness to forge signatures, modify signed documents without detection, or bypass security controls that rely on proper signature validation.
Security implications include potential data integrity compromise, unauthorized document modification, and breach of trust mechanisms within digital signature systems. The vulnerability creates opportunities for man-in-the-middle attacks where malicious actors could inject forged signatures into legitimate processes, undermining the entire digital signature infrastructure. This weakness particularly affects environments where document authenticity is paramount, such as legal proceedings, government communications, and financial transactions.
Mitigation strategies should focus on immediate patch deployment to all affected versions, implementing comprehensive cryptographic verification routines, and establishing proper exception handling for signature validation processes. Organizations should also consider implementing additional security layers including multi-factor authentication, enhanced monitoring of signature verification activities, and regular security assessments of digital signature systems. The remediation process must ensure complete replacement of vulnerable code segments with properly validated cryptographic libraries that adhere to industry standards such as those specified in NIST SP 800-57 for cryptographic key management and PKI implementations.
The vulnerability demonstrates the critical importance of robust cryptographic verification processes in security-sensitive applications, aligning with ATT&CK technique T1556.004 - "Modify Authentication Process" and emphasizing the need for proper input validation and error handling in cryptographic functions. Security teams should conduct thorough risk assessments to identify any systems relying on the affected libraries and ensure complete remediation across all digital signature processing environments.