CVE-2020-15522 in BC Java
Summary
by MITRE • 05/21/2021
Bouncy Castle BC Java before 1.66, BC C# .NET before 1.8.7, BC-FJA before 1.0.1.2, 1.0.2.1, and BC-FNA before 1.0.1.1 have a timing issue within the EC math library that can expose information about the private key when an attacker is able to observe timing information for the generation of multiple deterministic ECDSA signatures.
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Analysis
by VulDB Data Team • 07/17/2025
The vulnerability identified as CVE-2020-15522 represents a critical timing side-channel issue within the Bouncy Castle cryptographic library implementations across multiple platforms including Java, C# .NET, and specialized variants. This flaw resides in the elliptic curve mathematics library component that handles digital signature operations, specifically affecting the deterministic ECDSA signature generation process. The vulnerability stems from inconsistent execution times during cryptographic computations that can leak information about the private key through observable timing variations.
The technical implementation flaw manifests in the elliptic curve mathematical operations where the library performs different computational paths based on the input values, creating measurable timing differences that correlate with the private key bits. When an attacker can observe the time taken to generate multiple deterministic ECDSA signatures, they can exploit these timing variations to reconstruct the private key through statistical analysis and machine learning techniques. This timing leakage occurs because certain mathematical operations within the elliptic curve arithmetic do not execute in constant time, violating fundamental cryptographic principles for secure implementation.
The operational impact of this vulnerability extends across numerous applications that rely on Bouncy Castle for secure cryptographic operations, particularly those implementing digital signatures and certificate management. Systems using affected versions may be at risk when they generate multiple deterministic ECDSA signatures under conditions where timing information can be observed by attackers, including network-based timing attacks, local process monitoring, or even cloud environment side-channel attacks. The vulnerability affects a wide range of security protocols and applications that depend on elliptic curve cryptography for authentication and digital signature verification.
Mitigation strategies should prioritize immediate upgrading of all affected Bouncy Castle library versions to their patched releases, specifically Java versions 1.66 and above, C# .NET versions 1.8.7 and above, along with the corresponding BC-FJA and BC-FNA versions. Organizations should also implement monitoring for potential timing-based attacks and consider additional defensive measures such as constant-time implementation verification, randomizing signature generation timing, and ensuring proper isolation of cryptographic operations. This vulnerability aligns with CWE-385 and ATT&CK technique T1059.001, representing a classic side-channel attack vector that compromises cryptographic security through timing information leakage.