CVE-2025-6021 is a stack-based buffer overflow vulnerability identified in the xmlBuildQName function of the libxml2 library, a widely used XML parsing library integrated into many Linux distributions, including Red Hat Enterprise Linux 10. The root cause is an integer overflow during buffer size calculations, which leads to an incorrect allocation size and subsequently a stack-based buffer overflow when processing crafted XML input. This memory corruption can cause application crashes or denial of service conditions. The vulnerability is exploitable remotely over the network without requiring authentication or user interaction, increasing its risk profile. Although no known exploits have been reported in the wild, the vulnerability's characteristics—network vector, low attack complexity, and no privileges required—make it a critical concern for systems parsing untrusted XML data. The vulnerability affects Red Hat Enterprise Linux 10, a platform widely deployed in enterprise environments. The absence of patches at the time of disclosure necessitates immediate mitigation strategies to reduce exposure. The CVSS v3.1 score of 7.5 reflects the high impact on availability, with no direct impact on confidentiality or integrity. This vulnerability underscores the importance of secure input handling in XML processing libraries and the need for timely updates in critical infrastructure components.

For European organizations, the impact of CVE-2025-6021 can be significant, particularly for those relying on Red Hat Enterprise Linux 10 in production environments that process XML data from untrusted sources. Exploitation could lead to denial of service, causing service outages and operational disruptions. Memory corruption may also open avenues for further exploitation, potentially leading to system instability or escalation of attacks. Critical infrastructure, financial institutions, and government agencies using affected systems could face operational risks and reputational damage. The network-based attack vector means that exposed services parsing XML are vulnerable without requiring user credentials, increasing the attack surface. Given the widespread use of Red Hat Enterprise Linux in European data centers and cloud environments, the vulnerability could affect a broad range of sectors, including telecommunications, manufacturing, and public services. The lack of known exploits currently provides a window for proactive defense, but the high severity necessitates urgent mitigation to prevent potential exploitation.

1. Apply official patches from Red Hat as soon as they become available to address the vulnerability directly in libxml2. 2. Until patches are released, implement strict input validation and sanitization on all XML data sources to prevent processing of malformed or malicious XML payloads. 3. Restrict network exposure of services that parse XML, using firewalls and network segmentation to limit access to trusted sources only. 4. Employ runtime protections such as stack canaries, address space layout randomization (ASLR), and control flow integrity (CFI) to reduce the impact of potential buffer overflows. 5. Monitor logs and network traffic for unusual XML parsing errors or crashes that could indicate exploitation attempts. 6. Consider deploying application-layer gateways or XML firewalls that can detect and block malformed XML inputs. 7. Conduct thorough testing of applications relying on libxml2 to identify and remediate any unsafe XML processing code. 8. Maintain an incident response plan tailored to denial of service and memory corruption scenarios to ensure rapid recovery if exploitation occurs.