CVE-2022-39173 is a high-severity buffer overflow vulnerability found in wolfSSL versions prior to 5.5.1, specifically triggered during the TLS 1.3 handshake process. wolfSSL is a widely used lightweight SSL/TLS library designed for embedded systems and applications requiring secure communications. The vulnerability arises when a malicious client attempts to resume a previous TLS session. During this resumption, the handshake involves a Client Hello message followed by a Hello Retry Request (HRR) from the server, which requires the client to send a second Client Hello. The vulnerability is triggered if both Client Hello messages contain duplicate cipher suite lists. This unusual condition causes a buffer overflow due to improper handling of these duplicate cipher suites in the wolfSSL codebase. The overflow affects the availability of the service by potentially crashing the server or client application using wolfSSL, leading to denial-of-service (DoS). The CVSS 3.1 base score is 7.5, indicating a high severity level, with an attack vector of network (remote exploitation), no privileges required, and no user interaction needed. The vulnerability does not impact confidentiality or integrity but can cause service disruption. No known exploits in the wild have been reported as of the publication date. The underlying weakness is classified under CWE-787 (Out-of-bounds Write), a common and dangerous programming error that can lead to memory corruption. Since wolfSSL is embedded in many IoT devices, industrial control systems, and network appliances, this vulnerability could be exploited remotely by attackers to disrupt secure communications or cause application crashes during TLS 1.3 session resumption attempts.

For European organizations, the primary impact of CVE-2022-39173 is the potential for denial-of-service attacks against systems using vulnerable wolfSSL versions. This can disrupt critical services that rely on TLS 1.3 for secure communications, including IoT infrastructure, industrial automation, telecommunications, and embedded devices common in sectors such as manufacturing, energy, and healthcare. Although the vulnerability does not allow data theft or code execution, service outages can lead to operational downtime, loss of productivity, and potential safety risks in industrial environments. Given the increasing adoption of TLS 1.3 and wolfSSL in embedded and constrained devices across Europe, organizations could face targeted disruption attempts, especially in sectors where availability is critical. Additionally, the lack of user interaction and privileges required for exploitation means attackers can launch attacks remotely and at scale, increasing the risk of widespread service interruptions.

European organizations should prioritize upgrading wolfSSL to version 5.5.1 or later, where this vulnerability is patched. For embedded devices or systems where immediate patching is not feasible, network-level mitigations such as filtering or rate-limiting TLS handshake attempts that trigger session resumption with Hello Retry Requests can reduce exposure. Monitoring network traffic for unusual TLS handshake patterns involving duplicate cipher suites may help detect exploitation attempts. Vendors and integrators using wolfSSL in their products should issue firmware or software updates promptly. Additionally, organizations should conduct an inventory of devices and applications using wolfSSL to assess exposure and implement segmentation to isolate vulnerable systems. Employing robust incident response plans to quickly address potential denial-of-service events caused by this vulnerability is also recommended. Finally, security teams should stay informed about any emerging exploits or advisories related to this CVE.