CVE-2026-59647 in Bouncy Castle
Summary
by MITRE • 08/03/2026
In Bouncy Castle for Java before 1.85, CRMF/CMP password-MAC honours unbounded iteration count. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.12 (1.0.X series), 2.0.12 (2.0.X series) and 2.1.12 (2.1.X series).
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Analysis
by VulDB Data Team • 08/03/2026
The vulnerability in Bouncy Castle for Java represents a critical security flaw affecting multiple versions of the cryptographic library that handles Certificate Request Message Format and Certification Message Protocol operations. This issue specifically impacts password-based MAC (Message Authentication Code) implementations where the iteration count parameter is not properly bounded, creating a potential avenue for denial of service attacks and resource exhaustion scenarios. The vulnerability affects both standard and Long Term Support releases as well as FIPS-compliant versions, indicating a widespread impact across the library's various distributions.
The technical root cause stems from insufficient input validation within the CRMF/CMP password-MAC processing functionality where iteration counts are accepted without proper bounds checking. This allows attackers to specify arbitrarily large iteration values that can cause excessive computational overhead and resource consumption during MAC verification operations. The flaw operates at the cryptographic primitive level, specifically affecting password-based key derivation functions that are commonly used in certificate management protocols. When an attacker crafts a malicious request with an unbounded iteration count, the system processes this value without limitation, leading to exponential increases in processing time and memory consumption.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to potentially compromise system availability and performance across applications relying on Bouncy Castle for Java. Systems utilizing CRMF/CMP protocols for certificate enrollment and management become vulnerable to resource exhaustion attacks where attackers can consume excessive CPU cycles and memory resources through carefully crafted requests. This affects critical infrastructure components including certificate authorities, identity management systems, and any application processing certificate-related messages that depend on the vulnerable cryptographic library versions.
Mitigation strategies should prioritize immediate upgrades to patched versions of Bouncy Castle for Java, specifically targeting versions 1.85 and later for standard releases, 2.73.12 and later for LTS versions, and appropriate FIPS-compliant releases. Organizations should implement input validation controls at the application level to detect and reject excessively large iteration counts before they reach the cryptographic library functions. Network-level rate limiting and resource monitoring should be deployed to detect anomalous processing patterns that may indicate exploitation attempts. Security teams should also conduct comprehensive vulnerability assessments across all systems utilizing affected Bouncy Castle versions to identify potential exposure points and implement appropriate compensating controls. The vulnerability aligns with CWE-704 in the Common Weakness Enumeration catalog, which classifies improper input validation as a fundamental security weakness, and may map to ATT&CK techniques related to resource exhaustion and denial of service operations.