CVE-2016-1000338 in JCE Provider
Summary
by MITRE
In Bouncy Castle JCE Provider version 1.55 and earlier the DSA does not fully validate ASN.1 encoding of signature on verification. It is possible to inject extra elements in the sequence making up the signature and still have it validate, which in some cases may allow the introduction of 'invisible' data into a signed structure.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 09/13/2025
The vulnerability identified as CVE-2016-1000338 resides within the Bouncy Castle JCE Provider cryptographic library version 1.55 and earlier implementations. This flaw specifically affects the Digital Signature Algorithm (DSA) signature verification process, where the library fails to perform complete validation of ASN.1 encoding structures during signature verification operations. The issue stems from insufficient input sanitization and validation mechanisms that permit malformed ASN.1 sequences to pass verification checks, creating a potential security weakness in digital signature integrity.
The technical flaw manifests as a failure in ASN.1 structure validation during DSA signature verification, where the implementation accepts additional elements injected into the signature sequence without proper validation. This occurs because the cryptographic library does not strictly enforce the expected ASN.1 encoding format for DSA signatures, allowing attackers to manipulate the signature structure by injecting extra elements that do not interfere with the verification process but may contain hidden or malicious data. The vulnerability operates at the protocol level where ASN.1 encoding standards are not fully enforced, creating a gap in the signature validation mechanism that can be exploited to introduce invisible data modifications.
The operational impact of this vulnerability extends beyond simple signature validation failures, as it potentially enables attackers to manipulate signed data structures without detection. When DSA signatures are used for document integrity, code signing, or authentication purposes, this flaw could allow malicious actors to inject additional data into signed structures while maintaining apparent validity. The implications are particularly concerning in environments where cryptographic signatures are trusted to ensure data integrity and authenticity, as the vulnerability creates a covert channel for data injection that bypasses normal verification mechanisms. This weakness aligns with CWE-248, which addresses "Uncaught Exception" in software systems where improper handling of exceptional cases leads to security vulnerabilities.
Mitigation strategies for CVE-2016-1000338 require immediate upgrading to Bouncy Castle JCE Provider version 1.56 or later, where the ASN.1 validation has been corrected to properly enforce signature structure integrity. Organizations should also implement comprehensive signature validation monitoring to detect any anomalies in signature structures that may indicate exploitation attempts. Additionally, security teams should conduct thorough audits of cryptographic implementations to identify other potential ASN.1 validation weaknesses in related systems. The remediation process should include updating all affected applications that utilize the vulnerable Bouncy Castle library, implementing proper input validation at multiple layers, and establishing monitoring procedures to detect unauthorized modifications to signed data structures. This vulnerability demonstrates the critical importance of strict ASN.1 encoding validation in cryptographic systems and aligns with ATT&CK technique T1553.002, which covers "Subvert Trust Controls" through manipulation of cryptographic components.
The broader security implications of this vulnerability highlight the necessity of robust validation mechanisms in cryptographic libraries and underscore the potential for seemingly minor implementation flaws to create significant security risks. The flaw represents a failure in the principle of least privilege and proper input validation, where the cryptographic library should have enforced strict ASN.1 structure validation to prevent malformed signatures from being accepted as valid. This vulnerability serves as a reminder of the critical need for comprehensive security testing of cryptographic implementations and the importance of adhering to established cryptographic standards and best practices to prevent exploitation of validation weaknesses.