CVE-2023-5156 is a vulnerability identified in the GNU C Library component of Red Hat Enterprise Linux 6, introduced inadvertently by a recent fix addressing CVE-2023-4806. The flaw manifests as a missing release of allocated memory after its effective lifetime, resulting in a memory leak. Over time, this leak can cause applications relying on the affected library to exhaust available memory resources, leading to crashes or denial of service conditions. The vulnerability is exploitable remotely without requiring authentication or user interaction, increasing its risk profile. The CVSS v3.1 score of 7.5 reflects a high severity primarily due to its impact on availability (A:H), with no impact on confidentiality or integrity. While no known exploits have been reported in the wild, the presence of this flaw in a widely deployed enterprise operating system like RHEL 6 means that affected organizations could face service disruptions if exploited. The vulnerability is particularly concerning because it stems from a fix to a previous issue, highlighting the complexity of maintaining secure memory management in critical system libraries. The lack of patches at the time of publication necessitates interim mitigations to monitor and manage memory usage proactively.

For European organizations, the primary impact of CVE-2023-5156 is on system availability. Applications running on RHEL 6 that depend on the GNU C Library may experience memory exhaustion leading to crashes or denial of service, potentially disrupting critical business operations and services. This can affect enterprise environments, government agencies, and infrastructure providers still operating legacy RHEL 6 systems. Although confidentiality and integrity are not directly compromised, the operational disruption can have cascading effects, including loss of productivity, service outages, and increased operational costs. The vulnerability's remote exploitability without authentication means attackers can potentially trigger crashes from outside the network, increasing the risk of widespread denial of service attacks. Organizations with legacy systems or those that have delayed upgrades are at heightened risk. The absence of known exploits provides a window for proactive mitigation but also underscores the need for vigilance.

1. Apply official patches from Red Hat as soon as they become available to address the memory leak directly. 2. Until patches are released, implement monitoring of memory usage for critical applications and services running on RHEL 6 to detect abnormal consumption patterns early. 3. Limit network exposure of vulnerable services by using firewalls and network segmentation to reduce the attack surface. 4. Consider upgrading from RHEL 6 to a more recent, supported version of Red Hat Enterprise Linux to benefit from improved security and memory management. 5. Employ application-level watchdogs or automated restart mechanisms to recover services that crash due to memory exhaustion. 6. Conduct thorough testing of applications after patch deployment to ensure stability and performance. 7. Maintain an incident response plan that includes procedures for handling denial of service incidents related to memory leaks.