CVE-2023-49083 is a vulnerability classified under CWE-476 (NULL Pointer Dereference) found in the pyca cryptography package, a widely used Python library providing cryptographic primitives and recipes. The issue arises specifically when the functions load_pem_pkcs7_certificates or load_der_pkcs7_certificates are invoked to deserialize PKCS7 certificate blobs. Due to improper handling of certain malformed inputs, these functions may dereference a NULL pointer, leading to segmentation faults and crashing the hosting application. This results in a denial of service (DoS) condition, as the affected application becomes unavailable or unstable. The vulnerability affects all versions starting from 3.1 up to 41.0.6, where it has been fixed. The CVSS v3.1 base score is 5.9, reflecting a medium severity with network attack vector, no privileges required, no user interaction, but high attack complexity. The impact is limited to availability, with no confidentiality or integrity loss. Exploitation requires an attacker to supply crafted PKCS7 blobs to the vulnerable functions, which may be used in services or applications processing certificates, such as TLS termination points, certificate management systems, or security appliances using Python. No public exploits have been reported, but the risk of DoS in critical systems remains significant until patched.

For European organizations, this vulnerability poses a risk primarily to availability of systems that utilize the pyca cryptography package for handling PKCS7 certificates. This includes web servers, certificate validation services, security appliances, and internal tools that parse or manage certificates. A successful exploit could cause application crashes, leading to service interruptions and potential cascading failures in dependent systems. Sectors such as finance, healthcare, government, and critical infrastructure, which rely heavily on secure communications and certificate management, could experience operational disruptions. The DoS nature of the vulnerability means attackers can degrade service reliability without needing to breach confidentiality or integrity. Given the widespread use of Python in European IT environments, especially in automation and security tooling, unpatched systems may be vulnerable to targeted or opportunistic attacks. The absence of known exploits reduces immediate risk, but the medium severity and ease of triggering a crash warrant prompt remediation to maintain service continuity.

European organizations should immediately upgrade the pyca cryptography package to version 41.0.6 or later, where the vulnerability is patched. For environments where immediate upgrade is not feasible, implement input validation and sanitization on PKCS7 blobs before deserialization to detect and reject malformed or suspicious certificate data. Employ application-level monitoring and alerting to detect crashes or abnormal terminations related to certificate processing functions. Consider isolating certificate parsing components in sandboxed or containerized environments to limit impact of potential crashes. Review and harden any automated certificate management workflows that rely on pyca cryptography to ensure resilience against malformed inputs. Additionally, conduct thorough inventory and dependency analysis to identify all systems using affected versions of the package. Finally, maintain up-to-date backups and incident response plans to quickly recover from potential DoS incidents.