CVE-2011-1923 in PolarSSL
Summary
by MITRE
The Diffie-Hellman key-exchange implementation in dhm.c in PolarSSL before 0.14.2 does not properly validate a public parameter, which makes it easier for man-in-the-middle attackers to obtain the shared secret key by modifying network traffic, a related issue to CVE-2011-5095.
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Analysis
by VulDB Data Team • 12/04/2021
The vulnerability described in CVE-2011-1923 resides within the Diffie-Hellman key-exchange implementation of PolarSSL, a widely used open-source cryptographic library. This flaw affects versions prior to 0.14.2 and represents a significant weakness in the cryptographic protocol's security model. The issue stems from insufficient validation of public parameters during the Diffie-Hellman key exchange process, creating a pathway for attackers to manipulate network communications and potentially compromise the shared secret key that is fundamental to secure communications between parties.
The technical flaw manifests in the dhm.c file where the Diffie-Hellman implementation fails to properly validate the public parameter received from the remote party. This validation gap allows an attacker positioned in a man-in-the-middle position to modify the network traffic and inject malicious values into the Diffie-Hellman key exchange process. The vulnerability specifically relates to the lack of proper parameter validation, which should ensure that the public parameter falls within acceptable mathematical bounds and meets the cryptographic requirements for secure key generation. Without this validation, attackers can exploit the mathematical properties of Diffie-Hellman to manipulate the key exchange, potentially leading to successful attacks that compromise the confidentiality of communications.
From an operational perspective, this vulnerability creates a serious risk for any system utilizing PolarSSL versions before 0.14.2 in environments where man-in-the-middle attacks are possible. The impact extends beyond simple data interception, as successful exploitation could allow attackers to establish a false shared secret key, effectively breaking the encryption layer that protects communications. This vulnerability particularly affects systems that rely on secure key exchange for establishing secure connections, including web servers, VPN implementations, and any network services that utilize the Diffie-Hellman key exchange mechanism. The related vulnerability CVE-2011-5095 further emphasizes the broader category of issues affecting Diffie-Hellman implementations, highlighting the importance of proper parameter validation in cryptographic protocols.
The mitigation strategy for CVE-2011-1923 requires immediate upgrade to PolarSSL version 0.14.2 or later, which includes proper validation of Diffie-Hellman public parameters. Organizations should also implement network monitoring to detect unusual traffic patterns that might indicate attempted exploitation of this vulnerability. Security teams should conduct thorough inventory assessments to identify all systems using vulnerable PolarSSL versions and prioritize remediation efforts accordingly. Additionally, implementing proper cryptographic protocol validation and ensuring that all cryptographic libraries maintain up-to-date security practices are essential defensive measures. This vulnerability aligns with CWE-310, which addresses cryptographic weakness in parameter validation, and represents a clear violation of the principle of least privilege in cryptographic implementations where proper validation should be enforced at every stage of the key exchange process. The ATT&CK framework categorizes this as a cryptographic attack vector that leverages weaknesses in key exchange protocols, making it particularly relevant for organizations implementing secure communication frameworks.