CVE-2015-7940 in Business Intelligence Enterprise Edition
Summary
by MITRE
The Bouncy Castle Java library before 1.51 does not validate a point is withing the elliptic curve, which makes it easier for remote attackers to obtain private keys via a series of crafted elliptic curve Diffie Hellman (ECDH) key exchanges, aka an "invalid curve attack."
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Analysis
by VulDB Data Team • 09/13/2025
The Bouncy Castle Java library vulnerability CVE-2015-7940 represents a critical flaw in elliptic curve cryptography implementation that exposes systems to sophisticated attack vectors. This vulnerability affects versions prior to 1.51 and specifically targets the elliptic curve Diffie Hellman key exchange mechanism. The flaw stems from inadequate validation of elliptic curve points during cryptographic operations, creating a pathway for malicious actors to exploit the system's trust in mathematical curve properties. The vulnerability is particularly dangerous because it allows remote attackers to manipulate the key exchange process without requiring direct access to the cryptographic keys, making it a significant concern for secure communications infrastructure.
The technical root cause of this vulnerability lies in the absence of proper point validation within the elliptic curve arithmetic operations. When performing ECDH key exchanges, the library fails to verify that the public points provided by remote parties actually lie on the intended elliptic curve. This omission creates a mathematical exploit where attackers can submit points that appear valid but are actually on a different curve with weaker security properties. The flaw aligns with CWE-310, which addresses cryptographic issues related to insufficient validation of cryptographic parameters, and specifically relates to improper validation of cryptographic curves. This weakness enables what is known as an invalid curve attack, where the attacker manipulates the curve parameters to force the system into using a mathematically weaker curve that can be more easily broken.
The operational impact of this vulnerability extends far beyond simple cryptographic weakness, as it fundamentally undermines the security assumptions of elliptic curve cryptography implementations. Attackers can leverage this vulnerability to perform a series of carefully crafted ECDH key exchanges that gradually reveal information about the private keys, ultimately leading to complete key compromise. The attack requires multiple interactions but can be executed remotely without requiring privileged access or complex exploitation techniques. This makes it particularly dangerous for systems that rely on ECDH for secure communications, including web servers, VPN implementations, and any system using Bouncy Castle for cryptographic operations. The vulnerability affects the confidentiality and integrity of communications, potentially allowing attackers to decrypt sensitive data or impersonate legitimate parties within the cryptographic protocol.
Organizations utilizing the affected Bouncy Castle library should prioritize immediate remediation through version updates to 1.51 or later, which include proper point validation mechanisms. The mitigation strategy should also involve comprehensive security testing of all cryptographic implementations that depend on the library, particularly focusing on elliptic curve operations. System administrators should implement network monitoring to detect anomalous cryptographic behavior that might indicate exploitation attempts. Additionally, organizations should review their cryptographic protocols to ensure proper curve validation and consider implementing additional security layers such as certificate pinning or alternative cryptographic libraries where appropriate. This vulnerability demonstrates the critical importance of rigorous cryptographic implementation practices and adherence to established security standards, as even minor oversights in mathematical validation can lead to catastrophic security failures that compromise entire cryptographic ecosystems.