CVE-2023-4806 is a use-after-free vulnerability identified in the GNU C Library (glibc) component of Red Hat Enterprise Linux 8. The flaw occurs within the getaddrinfo function, which is responsible for resolving hostnames to IP addresses. Under very specific and rare conditions, getaddrinfo may access memory that has already been freed, leading to an application crash. This vulnerability is triggered only when a Name Service Switch (NSS) module implements the _nss_*_gethostbyname2_r and _nss_*_getcanonname_r hooks but does not implement the _nss_*_gethostbyname3_r hook. Additionally, the resolved hostname must return a large number of both IPv6 and IPv4 addresses, and the getaddrinfo call must specify the AF_INET6 address family with the flags AI_CANONNAME, AI_ALL, and AI_V4MAPPED. The consequence of this flaw is a denial-of-service (DoS) condition due to application crashes, as no direct confidentiality or integrity impact is reported. The vulnerability has a CVSS 3.1 base score of 5.9 (medium severity), with network attack vector, high attack complexity, no privileges required, no user interaction, and impact limited to availability. No known exploits are currently reported in the wild, and no patches or mitigations are linked in the provided data, though Red Hat typically issues updates for such vulnerabilities. This vulnerability affects Red Hat Enterprise Linux 8 systems using the vulnerable glibc version and specific NSS modules configured as described.

For European organizations, the primary impact of CVE-2023-4806 is the potential for denial-of-service conditions on critical systems running Red Hat Enterprise Linux 8 with the affected glibc and NSS module configurations. This could disrupt services relying on hostname resolution, such as web servers, application servers, and network services, potentially causing downtime and impacting business continuity. Since the vulnerability requires a rare configuration and specific usage patterns, widespread exploitation is unlikely; however, targeted attacks against critical infrastructure or high-value assets could leverage this to cause service interruptions. The lack of confidentiality or integrity impact reduces the risk of data breaches, but availability disruptions can still have significant operational and reputational consequences. Organizations in sectors with high reliance on Linux-based infrastructure, such as finance, telecommunications, government, and cloud service providers, may be more affected. The medium severity rating suggests that while the threat is not critical, it should not be ignored, especially in environments where uptime is critical.

1. Apply official patches and updates from Red Hat as soon as they become available to address the glibc vulnerability. 2. Audit NSS module configurations to identify any modules implementing only the _nss_*_gethostbyname2_r and _nss_*_getcanonname_r hooks without the _nss_*_gethostbyname3_r hook, and update or replace them with compliant versions. 3. Monitor and limit the use of getaddrinfo calls with the AF_INET6 address family combined with AI_CANONNAME, AI_ALL, and AI_V4MAPPED flags, especially in applications processing large numbers of IPv4 and IPv6 addresses. 4. Implement application-level monitoring to detect abnormal crashes or service disruptions related to hostname resolution functions. 5. Employ network-level protections to detect and block suspicious queries that might trigger the vulnerability, although exploitation complexity is high. 6. Conduct thorough testing in staging environments to verify that updates and configuration changes do not adversely affect system functionality. 7. Maintain an incident response plan to quickly address potential denial-of-service events stemming from this vulnerability.