CVE-2025-6021 identifies a stack-based buffer overflow vulnerability in the xmlBuildQName function of libxml2, a widely used XML parsing library included in Red Hat Enterprise Linux 10. The root cause is an integer overflow during buffer size calculations, which leads to the allocation of an insufficient buffer on the stack. When processing specially crafted XML input, this can cause a buffer overflow, resulting in memory corruption or a denial of service (DoS) condition. The vulnerability is remotely exploitable without requiring any privileges or user interaction, increasing its risk profile. Although no known exploits are currently reported in the wild, the flaw's presence in a core XML parsing library means that any application or service relying on libxml2 for XML processing on affected systems could be vulnerable. The vulnerability does not impact confidentiality or integrity directly but can severely affect availability by crashing processes or causing unpredictable behavior due to memory corruption. Red Hat Enterprise Linux 10 is the primary affected product, and organizations using this OS version should prioritize remediation. The vulnerability was published on June 12, 2025, with a CVSS v3.1 base score of 7.5, reflecting its high severity and ease of remote exploitation without authentication.

For European organizations, this vulnerability poses a significant risk to the availability and stability of systems running Red Hat Enterprise Linux 10, especially those processing XML data. Critical infrastructure sectors such as finance, telecommunications, government, and healthcare that rely on this OS and libxml2 for XML parsing could experience service outages or disruptions due to crashes or memory corruption. While the vulnerability does not directly compromise data confidentiality or integrity, denial of service conditions can lead to operational downtime, impacting business continuity and potentially causing financial and reputational damage. The remote and unauthenticated nature of the exploit increases the threat landscape, as attackers can trigger the vulnerability over the network without needing user credentials or interaction. This is particularly concerning for exposed services or applications that parse XML input from untrusted sources. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the potential for future exploitation. European organizations must assess their exposure based on their use of Red Hat Enterprise Linux 10 and libxml2-dependent applications.

Organizations should monitor Red Hat’s security advisories and apply official patches for libxml2 and Red Hat Enterprise Linux 10 as soon as they become available. Until patches are deployed, implementing network-level filtering to restrict access to services that process XML input can reduce exposure. Employing application-layer input validation and sanitization to detect and reject malformed XML can help mitigate exploitation attempts. Where feasible, sandboxing or isolating XML processing components limits the impact of potential crashes or memory corruption. Regularly updating and hardening systems, including disabling unnecessary XML processing services, reduces the attack surface. Security teams should also conduct vulnerability scanning and penetration testing focused on XML processing components to identify and remediate vulnerable instances. Monitoring logs for unusual crashes or memory errors related to XML parsing can provide early detection of exploitation attempts. Finally, organizations should prepare incident response plans to quickly address potential denial of service incidents stemming from this vulnerability.