CVE-2023-0217 is a high-severity vulnerability in OpenSSL version 3.0.0 involving an invalid pointer dereference during the processing of malformed DSA public keys. Specifically, the vulnerability arises in the EVP_PKEY_public_check() function, which is designed to validate public keys. When this function attempts to check a malformed DSA public key, it dereferences an invalid pointer on read, causing the application to crash. This behavior can be exploited by an attacker who supplies crafted malformed public keys to trigger a denial of service (DoS) condition. Notably, the core TLS implementation in OpenSSL does not invoke EVP_PKEY_public_check(), so typical TLS operations are not directly affected. However, applications that explicitly call this function—often to meet additional security requirements such as those mandated by standards like FIPS 140-3—are vulnerable. The vulnerability is classified under CWE-476 (NULL Pointer Dereference), which typically leads to application crashes and service interruptions. The CVSS v3.1 base score is 7.5 (high), reflecting the vulnerability's network attack vector, low attack complexity, no privileges or user interaction required, and its impact limited to availability (denial of service). There are no known exploits in the wild at the time of publication, and no official patches have been linked yet, indicating that mitigation may require updates from OpenSSL or application-level workarounds.

For European organizations, the primary impact of CVE-2023-0217 is the potential for denial of service attacks against applications using OpenSSL 3.0.0 that explicitly invoke EVP_PKEY_public_check() for DSA public key validation. Such applications may be found in environments with stringent cryptographic validation requirements, including government agencies, financial institutions, and critical infrastructure operators adhering to FIPS 140-3 or similar standards. A successful attack could disrupt services by crashing applications, leading to downtime and potential operational disruption. While confidentiality and integrity are not directly impacted, availability degradation can affect business continuity and trust. Organizations relying on OpenSSL 3.0.0 in custom or specialized cryptographic workflows are at higher risk. The absence of known exploits reduces immediate threat likelihood but does not eliminate risk, especially as attackers may develop exploits over time. The vulnerability's network exposure and lack of required authentication increase the risk profile, particularly for externally facing services or APIs that process untrusted public keys.

European organizations should take the following specific steps: 1) Identify and inventory all applications using OpenSSL 3.0.0, focusing on those that call EVP_PKEY_public_check() or perform explicit DSA public key validation. 2) Temporarily disable or avoid invoking EVP_PKEY_public_check() where possible, especially on untrusted inputs, until a patched OpenSSL version is available. 3) Implement input validation and sanitization to reject malformed DSA public keys before they reach the vulnerable function. 4) Monitor application logs and crash reports for signs of exploitation attempts or abnormal terminations related to public key processing. 5) Engage with OpenSSL maintainers and track official security advisories for patches or updates addressing this vulnerability. 6) For environments requiring FIPS 140-3 compliance, review cryptographic policy configurations to balance security requirements with exposure to this vulnerability. 7) Employ network-level protections such as rate limiting and filtering to reduce the risk of automated or mass exploitation attempts. 8) Prepare incident response plans to quickly address potential denial of service incidents linked to this vulnerability.