CVE-2016-4407 in SAPCRYPTOLIB
Summary
by MITRE
The DSA algorithm implementation in SAP SAPCRYPTOLIB 5.555.38 does not properly check signatures, which allows remote authenticated users to impersonate arbitrary users via unspecified vectors, aka SAP Security Note 2223008.
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Analysis
by VulDB Data Team • 05/07/2019
The vulnerability identified as CVE-2016-4407 resides within the Digital Signature Algorithm implementation of SAPCRYPTOLIB version 5.55.38, representing a critical security flaw that undermines the integrity of digital signatures used in SAP systems. This weakness specifically affects the cryptographic verification process where the system fails to properly validate the authenticity of digital signatures generated using the DSA algorithm. The flaw enables authenticated attackers to exploit the system's signature validation mechanism, potentially allowing them to forge signatures and gain unauthorized access to SAP environments. The vulnerability stems from inadequate input validation and verification procedures within the cryptographic library, creating a pathway for malicious actors to manipulate signature checks without detection.
The technical implementation flaw manifests in the insufficient validation of DSA signature parameters during the verification process. When the SAPCRYPTOLIB library processes digital signatures, it does not adequately verify the mathematical relationships between the signature components and the public key, allowing forged signatures to pass validation checks. This cryptographic weakness aligns with CWE-327, which addresses the use of weak or broken cryptographic algorithms, and specifically relates to improper implementation of signature verification routines. The vulnerability can be exploited through various attack vectors that leverage the authenticated user context, as the flaw requires only legitimate access to the system to manipulate signature validation outcomes. Attackers can potentially impersonate any user within the system by generating valid-looking signatures that bypass the integrity checks.
The operational impact of this vulnerability extends beyond simple authentication bypass, as it compromises the fundamental security model of SAP systems that rely on digital signatures for user authentication and data integrity. An attacker who successfully exploits this vulnerability can assume the identity of any legitimate user within the SAP environment, potentially gaining access to sensitive data, modifying critical business processes, or executing unauthorized transactions. The implications are particularly severe in enterprise environments where SAP systems handle financial data, customer information, and operational controls. This vulnerability directly impacts the CIA triad by weakening integrity and authentication mechanisms, allowing for unauthorized access and potential data manipulation. The attack can be executed remotely through authenticated sessions, making it particularly dangerous in networked environments where system access can be gained through various legitimate entry points.
Organizations affected by CVE-2016-4407 should implement immediate mitigation strategies including applying the relevant SAP security note 2223008, which provides the official patch for the cryptographic library. System administrators should also conduct comprehensive vulnerability assessments to identify all instances of SAPCRYPTOLIB 5.55.38 within their infrastructure and ensure proper patch management protocols are followed. Additional security measures include monitoring authentication logs for suspicious signature validation activities and implementing network segmentation to limit the attack surface. The vulnerability demonstrates the critical importance of proper cryptographic implementation and validation, aligning with ATT&CK technique T1552.004 for credentials from password storage devices, as the compromised signature validation essentially allows attackers to extract and abuse authentication credentials. Organizations should also consider implementing additional authentication layers such as multi-factor authentication to reduce the risk of exploitation and maintain overall system security posture.