CVE-2023-4527 is a stack-based buffer overflow vulnerability identified in the GNU C Library (glibc) component of Red Hat Enterprise Linux 8. The flaw manifests when the getaddrinfo function is invoked with the AF_UNSPEC address family, and the system's DNS resolver is configured with the no-aaaa option in /etc/resolv.conf, which disables IPv6 AAAA queries. Under these conditions, if a DNS response received over TCP exceeds 2048 bytes, the function may improperly handle the response, leading to potential disclosure of stack memory contents via the function's returned address data. This can also cause the application or system process to crash, impacting availability. The vulnerability does not require any privileges or user interaction to exploit but has a high attack complexity because it depends on specific DNS resolver configurations and unusually large DNS responses. The CVSS v3.1 base score is 6.5, reflecting a medium severity with network attack vector, high complexity, no privileges required, no user interaction, unchanged scope, limited confidentiality impact, no integrity impact, and high availability impact. There are no known public exploits or active exploitation reported at this time. The vulnerability affects systems running Red Hat Enterprise Linux 8 with the vulnerable glibc version and configured with no-aaaa mode in DNS resolver settings. Since glibc is a core system library used by many applications, the impact can be widespread on affected systems. The primary risk is denial of service due to crashes, with some risk of information disclosure of stack contents, which could potentially aid further exploitation. The vulnerability highlights the importance of secure DNS resolver configurations and timely patching of critical system libraries.

For European organizations, the primary impact of CVE-2023-4527 is on system availability due to potential crashes triggered by crafted DNS responses. Organizations relying on Red Hat Enterprise Linux 8 in critical infrastructure, enterprise servers, or cloud environments may experience service disruptions if exploited. The limited confidentiality impact means sensitive data leakage risk is low but not negligible, as stack contents could reveal some memory information. The requirement for specific DNS resolver configuration (no-aaaa mode) and large DNS responses reduces the likelihood of widespread exploitation but does not eliminate risk, especially in environments with customized DNS settings or where attackers can influence DNS responses. Disruptions could affect sectors such as finance, telecommunications, government, and energy, where Linux servers are prevalent. Additionally, denial of service conditions could be leveraged as part of multi-stage attacks or to degrade service availability during targeted campaigns. The absence of known exploits provides a window for mitigation, but organizations should act promptly to avoid exposure. The vulnerability also underscores the need for careful DNS resolver configuration management and monitoring of DNS traffic anomalies.

1. Apply official patches or updates from Red Hat as soon as they become available to address the glibc vulnerability. 2. Review and modify DNS resolver configurations to avoid using no-aaaa mode unless absolutely necessary, as this setting contributes to the vulnerability. 3. Implement DNS response size limits or filtering at network boundaries to block unusually large DNS responses over TCP that exceed 2048 bytes. 4. Monitor DNS traffic for anomalies, including large TCP DNS responses, which could indicate attempted exploitation. 5. Employ runtime protections such as stack canaries, address space layout randomization (ASLR), and control flow integrity (CFI) to reduce the impact of buffer overflows. 6. Conduct regular vulnerability scanning and configuration audits on Red Hat Enterprise Linux 8 systems to detect vulnerable glibc versions and risky DNS settings. 7. Prepare incident response plans to quickly address potential denial of service events linked to this vulnerability. 8. Where possible, isolate critical systems from untrusted DNS servers or networks to limit exposure to malicious DNS responses. 9. Educate system administrators about the risks of DNS resolver configurations and the importance of timely patching.