CVE-2017-13098 in TLS
Summary
by MITRE
BouncyCastle TLS prior to version 1.0.3, when configured to use the JCE (Java Cryptography Extension) for cryptographic functions, provides a weak Bleichenbacher oracle when any TLS cipher suite using RSA key exchange is negotiated. An attacker can recover the private key from a vulnerable application. This vulnerability is referred to as "ROBOT."
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Analysis
by VulDB Data Team • 05/12/2025
The vulnerability identified as CVE-2017-13098 represents a critical weakness in the BouncyCastle TLS implementation that affects versions prior to 1.0.3. This flaw specifically manifests when the library is configured to utilize Java Cryptography Extension for cryptographic operations, creating a significant security risk that has been categorized under the broader class of cryptographic vulnerabilities. The vulnerability operates through a sophisticated attack vector that exploits weaknesses in the RSA key exchange mechanism within TLS protocols, making it particularly dangerous for applications that rely on secure communication channels. The issue was subsequently named "ROBOT" which stands for RSA Oracle Bombing TOol, highlighting its nature as a cryptographic oracle attack that can be exploited by adversaries to compromise the security of encrypted communications.
The technical flaw underlying CVE-2017-13098 stems from the implementation of a weak Bleichenbacher oracle within the BouncyCastle TLS library. This oracle provides attackers with information about the validity of RSA decryption operations through timing or error response differences, which can be systematically exploited to reconstruct the private key. The vulnerability specifically affects TLS cipher suites that utilize RSA key exchange, where the oracle's weakness becomes apparent during the handshake process. When an attacker successfully exploits this vulnerability, they can iteratively query the system to determine the private key components through mathematical analysis of the oracle responses, ultimately leading to complete private key recovery. This represents a fundamental breakdown in the cryptographic security assumptions that TLS protocols rely upon for maintaining confidentiality and authentication.
The operational impact of this vulnerability extends far beyond simple cryptographic weakness, as it fundamentally undermines the security of any application that depends on BouncyCastle TLS for secure communications. Organizations using vulnerable versions of the library face potential exposure of their private keys, which can lead to complete compromise of their encrypted communications, identity theft, and unauthorized access to sensitive data. The vulnerability is particularly concerning because it allows attackers to perform key recovery attacks without requiring direct access to the target system, making it a significant threat to web servers, email systems, and any infrastructure that relies on RSA-based TLS implementations. The attack can be executed remotely and systematically, making it a persistent threat that can be exploited by threat actors with minimal resources and technical expertise.
Mitigation strategies for CVE-2017-13098 primarily focus on upgrading to BouncyCastle version 1.0.3 or later, which contains the necessary fixes to address the weak oracle implementation. Organizations should also consider implementing immediate temporary measures such as disabling RSA key exchange cipher suites in their TLS configurations until the upgrade is complete. Security teams must conduct comprehensive inventory assessments to identify all systems using vulnerable BouncyCastle versions and prioritize remediation efforts accordingly. The vulnerability aligns with CWE-310, which classifies it as a weakness related to cryptographic implementation, and maps to ATT&CK technique T1552.001 for credential access through the exploitation of cryptographic weaknesses. Additionally, organizations should consider implementing monitoring and detection capabilities to identify potential exploitation attempts, as the attack can be automated and may not be immediately apparent to system administrators. Regular security assessments and vulnerability scanning should be conducted to ensure that no other cryptographic weaknesses exist within the infrastructure that could be exploited in conjunction with this vulnerability.