CVE-2022-3602 is a high-severity buffer overflow vulnerability found in OpenSSL versions 3.0.0 through 3.0.6, specifically within the X.509 certificate verification process during name constraint checking. The flaw arises when processing a maliciously crafted email address in a certificate, allowing an attacker to overflow four bytes on the stack. This vulnerability can be triggered in two main scenarios: a TLS client connecting to a malicious server presenting a crafted certificate, or a TLS server requesting client authentication where a malicious client provides a crafted certificate. Exploitation requires either that a Certificate Authority (CA) has signed the malicious certificate or that the application continues verification despite failing to build a trusted certificate chain. The buffer overflow can cause a denial of service via a crash or potentially enable remote code execution. However, many platforms' stack overflow protections and compiler-specific stack layouts reduce the likelihood of successful remote code execution. The vulnerability was initially rated as critical but was downgraded to high severity after considering these mitigating factors. The issue is fixed in OpenSSL version 3.0.7. The CVSS v3.1 base score is 7.5, reflecting a network attack vector with no privileges or user interaction required, but impacting availability only. No known exploits are currently reported in the wild. This vulnerability is categorized under CWE-787 (Out-of-bounds Write).

For European organizations, the impact of CVE-2022-3602 can be significant due to the widespread use of OpenSSL in numerous applications and services, including web servers, email servers, VPNs, and other TLS-enabled services. A successful exploitation could lead to denial of service, disrupting critical services and causing operational downtime. Although remote code execution is theoretically possible, it is mitigated by platform protections, reducing the immediate risk of full system compromise. However, denial of service attacks could still affect availability of services, potentially impacting business continuity, especially in sectors reliant on secure communications such as finance, healthcare, and government. The requirement for a malicious certificate signed by a trusted CA or continued verification despite chain failure limits the attack surface but does not eliminate it. Organizations using OpenSSL 3.0.x versions should consider this vulnerability a serious risk and prioritize patching to avoid service disruptions and potential exploitation.

European organizations should immediately upgrade all OpenSSL 3.0.x deployments to version 3.0.7 or later to remediate this vulnerability. Beyond patching, organizations should implement strict certificate validation policies to reject certificates that fail chain verification, reducing the risk of accepting malicious certificates. Network defenses such as TLS interception and inspection can help detect anomalous certificates. Additionally, enabling and enforcing client certificate authentication only when necessary can minimize exposure. Employing runtime protections like stack canaries, address space layout randomization (ASLR), and control flow integrity (CFI) can further mitigate exploitation risks. Regular vulnerability scanning and monitoring for unusual TLS handshake failures or crashes can help detect attempted exploitation. Finally, organizations should maintain an inventory of systems using OpenSSL 3.0.x to ensure comprehensive patch coverage.