CVE-2018-15836 in Openswan
Summary
by MITRE
In Openswan before 2.6.50.1, IKEv2 signature verification is vulnerable to "Variants of Bleichenbacher's Low-Exponent Attack on PKCS#1 RSA Signatures" attacks when RAW RSA keys are used.
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Analysis
by VulDB Data Team • 05/19/2023
The vulnerability identified as CVE-2018-15836 affects Openswan versions prior to 2.6.50.1 and specifically targets the IKEv2 signature verification mechanism. This flaw represents a critical cryptographic weakness that exploits known vulnerabilities in RSA signature verification when raw RSA keys are employed in the Internet Key Exchange version 2 protocol. The issue stems from the implementation's susceptibility to Bleichenbacher's low-exponent attack variants, which have been well-documented in cryptographic literature and pose significant risks to secure communications infrastructure.
The technical implementation flaw resides in how Openswan handles RSA signature verification during IKEv2 exchanges when raw RSA keys are configured. This vulnerability allows attackers to perform chosen-ciphertext attacks against the RSA signatures, potentially enabling them to forge signatures or extract private key information. The attack exploits the mathematical properties of RSA encryption when low public exponents are used, combined with the lack of proper padding validation in the signature verification process. This weakness specifically impacts systems that have not implemented proper cryptographic countermeasures against known RSA signature vulnerabilities.
The operational impact of this vulnerability extends beyond simple authentication failures, as it can enable man-in-the-middle attacks and compromise the integrity of secure communications channels established through IKEv2. An attacker capable of exploiting this vulnerability could potentially decrypt communications, modify traffic, or impersonate legitimate entities within the secured network. The risk is particularly severe for organizations relying on Openswan for IPsec VPN implementations, as the vulnerability affects the fundamental security guarantees provided by the IKEv2 protocol. This weakness can lead to complete compromise of the encrypted communication infrastructure, making it a high-priority issue for security teams managing network security appliances and VPN gateways.
Organizations should immediately upgrade to Openswan version 2.6.50.1 or later to address this vulnerability, as the patch includes proper cryptographic implementations that mitigate the Bleichenbacher attack variants. System administrators should also review their IKEv2 configurations to ensure that raw RSA keys are not being used unnecessarily, and consider implementing additional cryptographic protections such as certificate-based authentication or stronger key management practices. The vulnerability aligns with CWE-327, which addresses weak cryptographic algorithms and improper implementation of cryptographic functions, and represents a clear violation of the principle of least privilege in cryptographic operations. Security teams should monitor their networks for potential exploitation attempts and implement network segmentation to limit the impact of any successful attacks. This vulnerability also maps to ATT&CK technique T1552.001, which involves unsecured credentials and weak cryptographic implementations that can lead to credential compromise and unauthorized access to network resources.