CVE-2017-1000385 in otp TLS Server
Summary
by MITRE
The Erlang otp TLS server answers with different TLS alerts to different error types in the RSA PKCS #1 1.5 padding. This allows an attacker to decrypt content or sign messages with the server's private key (this is a variation of the Bleichenbacher attack).
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 12/26/2024
The vulnerability identified as CVE-2017-1000385 resides within the Erlang OTP TLS implementation, specifically affecting how the system handles RSA PKCS #1 1.5 padding errors during TLS handshakes. This flaw represents a critical security weakness that enables attackers to exploit timing differences in TLS alert responses to perform cryptographic attacks against the server's private key. The vulnerability manifests when the TLS server responds with distinct error messages for different types of padding errors, creating observable patterns that can be leveraged by malicious actors.
The technical mechanism underlying this vulnerability stems from the inconsistent error handling within the RSA PKCS #1 1.5 padding validation process. When the TLS server encounters invalid padding during decryption operations, it provides different TLS alert responses depending on whether the padding is malformed or the decryption fails due to other factors. This differential response creates timing variations that attackers can measure and analyze to reconstruct the private key through a process similar to the well-known Bleichenbacher attack. The vulnerability specifically affects the RSA decryption operations during the TLS handshake process, where the server validates client certificates and handles encrypted data.
From an operational impact perspective, this vulnerability presents a severe risk to systems relying on Erlang OTP TLS implementations, particularly those handling sensitive data or serving as certificate authorities. Attackers can exploit this weakness to decrypt confidential communications, forge digital signatures, or impersonate legitimate server entities. The attack requires significant computational resources and time to execute successfully, but once completed, it provides complete access to the server's private key, enabling long-term compromise of encrypted communications. This vulnerability affects various Erlang versions and can be particularly dangerous in environments where the server handles financial transactions, personal data, or other sensitive information requiring strong cryptographic protection.
The security implications of this vulnerability align with CWE-310, which addresses cryptographic weaknesses related to improper implementation of cryptographic protocols, and can be categorized under ATT&CK technique T1552.004 for unsecured credentials. The attack vector requires a man-in-the-middle position or access to the TLS communication channel to observe the timing differences in error responses. Mitigation strategies include implementing constant-time error handling for padding validation, upgrading to patched versions of Erlang OTP that address this specific issue, and deploying additional monitoring to detect anomalous TLS alert patterns. Organizations should also consider implementing proper cryptographic key management practices and regularly updating their systems to address known vulnerabilities in cryptographic libraries and implementations.