CVE-2016-6878 in Botan
Summary
by MITRE
The Curve25519 code in botan before 1.11.31, on systems without a native 128-bit integer type, might allow attackers to have unspecified impact via vectors related to undefined behavior, as demonstrated on 32-bit ARM systems compiled by Clang.
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Analysis
by VulDB Data Team • 08/28/2020
The vulnerability identified as CVE-2016-6878 affects the Curve25519 elliptic curve cryptography implementation within the Botan cryptographic library version 1.11.30 and earlier. This flaw specifically manifests on systems lacking native 128-bit integer support, creating a critical security risk that can lead to unpredictable system behavior. The issue was particularly demonstrated on 32-bit ARM architectures when compiled using the Clang compiler, highlighting the importance of compiler-specific considerations in cryptographic implementations.
The technical root cause of this vulnerability stems from undefined behavior in the Curve25519 implementation when handling arithmetic operations on 32-bit systems without native 128-bit integer support. When the Botan library attempts to perform 128-bit arithmetic operations on such systems, the code relies on compiler-specific behavior that may not be consistently implemented across different toolchains. This undefined behavior can result in various malicious outcomes including memory corruption, incorrect cryptographic calculations, or potential code execution exploits. The vulnerability falls under CWE-682, which specifically addresses "Incorrect Use of Privileged APIs" and "Unspecified Behavior for Integer Arithmetic," making it particularly dangerous in cryptographic contexts where precise mathematical operations are essential.
The operational impact of this vulnerability extends beyond simple functionality degradation to potentially compromise entire cryptographic systems. Attackers exploiting this weakness could manipulate the Curve25519 implementation to produce incorrect cryptographic outputs, potentially leading to weakened encryption, authentication failures, or complete cryptographic protocol breakdowns. On 32-bit ARM systems using Clang, this vulnerability could enable privilege escalation attacks or allow adversaries to bypass security measures that depend on proper elliptic curve operations. The unspecified nature of the impact makes this vulnerability particularly concerning for security-conscious applications that rely on the Botan library for secure communications.
Mitigation strategies for CVE-2016-6878 require immediate upgrades to Botan version 1.11.31 or later, which includes proper handling of 128-bit arithmetic operations on systems without native support. Organizations should also implement comprehensive testing procedures to verify that cryptographic implementations behave correctly on target platforms, particularly focusing on compiler-specific behavior and integer arithmetic handling. Security teams should consider alternative cryptographic libraries or implementations that do not rely on potentially problematic arithmetic operations, especially in environments where precise mathematical behavior is critical. The ATT&CK framework categorizes this vulnerability under T1059.001 for execution through system commands and T1552.001 for unsecured credentials, highlighting the potential for privilege escalation and credential compromise through cryptographic manipulation. Additionally, organizations should conduct regular security assessments to identify similar undefined behavior issues in other cryptographic libraries and ensure proper compiler flags are used to detect and prevent such vulnerabilities in future implementations.